SRON_Spectrum_2016

SPECTRUM NO. 18 

MARCH 2016 

DISTANT PLANETS 

THROW LIGHT ON EARTH 

SEARCHING FOR ANSWERS 

IN THE HOT UNIVERSE 

AEROSOLS: MISSING LINK 

IN CLIMATE RESEARCH

Veni for research into cosmic structures 

SRON astronomer Hiroki Akamatsu has 

budget of clusters and the contribution this 

2 

SRON Spectrum 

Content 

received a Veni grant worth 250,000 

euros from the Netherlands Organisation 

for Scientific Research (NWO) to investigate 

the evolution of cosmic structures. 

For this, Akamatsu will make use of the 

new Japanese space telescope ASTRO-H 

(now called: Hitomi). In addition, he will 

contribute to the development of a new 

‘imaging spectrometer’ for the large successor 

of ASTRO-H, the space telescope 

ATHENA (ESA). 

makes to the formation of cosmic structures. 

Secondly he will focus on developing a 

power ful X-ray spectrometer for the space 

telescope ATHENA. The spectrometer can be 

used for astronomical missions but is also important 

for materials sciences, for example. 

Short news ............................................ 2 

Using small blocks to find 

large waves........................................... 6 

Distant planets shed light 

on earth............................................... 10 

OOne of the major questions in modern-day 

astronomy is how cosmic structures are 

formed. These largely evolve at the inter - 

sections of the cosmic web that also harbor 

large clusters of galaxies. In these clusters the 

most visible (baryonic) material in the universe 

is also found in the form of hot plasma 

(T~10 6 -10 8 K). This hot plasma emits a lot 

of X-rays and Akamatsu will study these. 

He will first of all concentrate on the energy 

Artist’s impression of ASTRO-H, also called Hitomi 

(Akihiro Ikeshita/JAXA). 

Tropomi ready for transport to Russia 

Searching for answers in 

the hot universe.................................. 12 

Aerosols: missing link in 

climate research .................................. 15 

SPEX-airborne ready for NASA 

test flight ............................................ 17 

Wouter blogs... From the South Pole 

to the edge of the universe .............. 20 

The missions to date........................... 28 

After a successful integration with the 

satellite, the Dutch earth observation 

instrument Tropomi is now ready for 

transport to Plesetsk in Russia. From 

the third quarter of 2016 onwards the 

European earth observation mission will 

collect very accurate data worldwide 

about our climate and air quality. 

2015 was a busy and exciting year for the 

Tropomi partners. After a successful assembly 

at Airbus Defence and Space in Stevenage the 

entire earth observation satellite was shipped 

to Toulouse in July last year where Intespace 

subjected it to an extensive test program. 

Both the satellite and instrument passed this 

with good marks. The satellite has now re - 

turned to Stevenage where it is being pre - 

pared for the transport to the launch base in 

Plesetsk, Russia. There, Tropomi will be 

launched this autumn onboard 

a Russian Rockot 

launcher. 

Tropomi detects sunlight 

that is reflected by the atmosphere 

and compares this 

with light directly from the

S H O R T N E W S 

sun. The sunlight is reflected via mirrors, un - 

rav eled by gratings and eventually recorded 

with a detector. Thanks to Dutch innovations 

like the immersed grating of SRON and TNO, 

the infrared spectrometer is 40 times smaller 

than its predecessor (which was equipped 

with a conventional grating) without compromising 

the precision. 

The data collected by Tropomi in space are 

processed by KNMI, SRON, and others and 

then made suitable for scientific research and 

other applications. Parallel to the preparations 

for the hardware, a Dutch team from Airbus 

Defence and Space and KNMI are working on 

the operational aspects of the ground segment 

of the mission at ESOC, the European Space 

Operations Centre in Darmstadt, Germany. 

3 


Millions for medium-sized black holes 

SRON researcher Peter Jonker has been 

awarded a prestigious grant worth 

2 million euros by the European Research 

Council for research into the existence 

of medium-sized black holes. 

With Whis group, Jonker will tackle one of the 

big mysteries of high-energy physics: 

do medium-sized black holes actually exist? 

Astronomers think that these elusive mediumsized 

black holes – with a mass of hundreds 

to hundreds of thousands of solar masses – 

must have evolved early in the history of the 

universe from the first generation of superstars 

or from enormous gas clouds that collapsed 

into black holes. Accordingly space 

around galaxies should be full of them, in - 

clud ing the space around our own Milky Way. 

There are now strong indications for the existence 

of medium-sized black holes but there 

is no direct evidence yet. 

Jonker therefore wants to use ESA’s new 

space telescope Gaia and the largest tele - 

scopes on earth to study objects and phe - 

nom ena that can only have arisen due to the 

activity of a medium-sized black hole. This 

concerns ultracompact receding clusters, red 

supergiant’s that feed extremely clear X-ray 

sources, and white dwarfs that are pulled 

apart by tidal forces. Jonker is searching for 

Artist’s impression of the Gaia space telescope (ESA/ATG 

medialab; background: ESO/S. Brunier). 

stars located in the sphere of influence of 

a candidate medium-sized black hole. By 

measuring their movements he can determine 

the mass of the black hole. 

Gelderland invests in Smart Space Cluster 

The Province of Gelderland is investing 

195,000 euros in establishing a Smart 

Space Cluster, which develops innovative 

products for the space sector. In the 

cluster – in which SRON is participating – 

companies are working together with 

knowledge institutions. The sophisticated 

space technology must also be usable in 

health care, nutrition, and the manufac - 

turing industry. 

I 

In the coming period the Smart Space Cluster 

partners will work on innovative space tech - 

niques that can subsequently also have spin-off 

applications on earth. This must result in new 

projects that generate extra jobs. 

Besides SRON, the Smart Space Cluster participants 

are the companies Q-Concepts, PMP, 

Prange, Veldlaser, Sumipro, Inspiro, and Mecon. 

NOVA, Radboud University, and the University 

of Twente are also taking part. The platform 

will be further expanded in the coming period. 

The project must result in five business cases 

that can be further developed and marketed 

and in a platform where the knowledge can 

be shared. SRON is acting as the launching cus- 

The project participants of the Smart Space Cluster with the 

representative of the Province of Gelderland (QConcepts). 

tomer in this cluster, in other words parts of 

SRON hardware projects will be contributed.

‘The second earth’ unveiled in NEMO 

4 


On the afternoon of Wednesday, 27 Janu - 

ary 2016 ‘The second earth’ was officially 

opened at Science Center NEMO. SRON is 

sponsoring this exhibit, which is part of 

the exhibition ‘Searching for life’. 

T‘The second earth’ specifically focuses on the 

habitable zone around a star. In the exhibit, 

visitors can change the position of a planet 

in the habitable zone around a star like our 

sun and then experience what happens. On 

a screen they also receive information about 

the changed living conditions on the planet. 

The research into exoplanets, planets around 

stars other than our sun, is a new line of research 

for SRON. The institute is mainly focus - 

ing on analyzing exoplanet atmospheres in 

collaboration with other Dutch institutes and 

universities. The exhibit at NEMO brings this 

new focus area to life. 

After a word of welcome by SRON director 

Roel Gathier, three exoplanet researchers gave 

presentations. Michiel Min (SRON) considered 

whether we are alone in the universe, Frans 

Snik (Leiden University) said something about 

the research into rainbows on exoplanets, and 

Wim van Westrenen (VU University Amsterdam) 

compared planetary research within and 

outside of our solar system. Then ‘The second 

earth’ was ceremoniously opened by Amito 

Haarhuis (deputy director NEMO) and Roel 

Gathier (SRON). 

European grant for revolutionary red-shift machine 

With funding from the European Research 

Council (2.4 million euros) SRON 

researcher Jochem Baselmans will 

de velop a revolutionary instrument to 

measure the red shift of so-called sub - 

milli meter galaxies. 

VVisible and/or ultraviolet light emitted by distant 

galaxies is visible in the infrared due to 

the red shift. These galaxies are known as 

submillimeter galaxies. The instrument that 

Baselmans will develop – MOSAIC (Multi 

Object Spectrometer with an Array of superconducting 

Integrated Circuits) – will soon be 

able to simultaneously measure the emission 

spectrum of no less than 25 of these galaxies 

over an enormous bandwidth. MOSAIC will 

therefore make it possible to realize a syste m - 

a tic study of the enormous number of submillimeter 

galaxies, something that is unfeasible 

at present. 

With the ‘red–shift machine’ Baselmans and 

his team hope to obtain a lot of new infor - 

mation about the evolution of galaxies. The 

instrument will also enable astronomers to 

measure the distance to these galaxies. 

The heart of MOSAIC consists of an array of 

25 pixels that capture infrared or submilli - 

meter radiation in a frequency range of 325- 

905 GHz. Each pixel has an antenna that can 

change its direction of observation. This 

means that MOSAIC can point each pixel 

independently to an individual galaxy. 

A high-resolution spectrometer (R=500) 

located behind the antenna measures the 

galaxy’s spectrum. All of these functionalities 

are combined in a single chip that is based 

on superconducting nanotechnology. 

MOSAIC is being developed in collaboration 

with Delft University of Technology and the 

Leiden Observatory. The observations will be 

made using the Japanese telescope ASTE in 

Chile. 

The heart of MOSAIC consists of an array of 

25 pixels. Each pixel has an antenna that can 

change its direction of observation. 

This means that MOSAIC can point each pixel (A) 

independently to an individual galaxy. A highresolution 

spectrometer (R=500) located behind 

the antennae measures the galaxy’s spectrum (B).

More collaboration with China 

In the past year several more important 

steps have been taken towards a structural 

collaboration with the Chinese 

space sector. SRON is involved in this 

together with TNO, NSO, the Dutch 

government, and other Dutch space organizations 

and institutes. A possible CO 2 

mission to be realized with Chinese fund - 

ing is of particular interest. 

CChina is already an important player in the 

international aerospace industry but the Chinese 

government wants to strengthen that 

position even further still. China is therefore 

seeking active collaboration with experienced 

international partners. The long-term goal is 

for the Netherlands and China to collaborate 

on the design and development of new space 

instruments and the use of these by science 

and society. In 2014, TNO and the Beijing 

Institute of Space Machinery and Electronics 

(BISME) established a joint China lab. In May 

2015 this led to the signing of a collaboration 

agreement (INSET) by a cluster of Dutch space 

companies and institutes that focus on the 

Chinese market and are therefore seeking a 

closer collaboration. 

The parties involved are TNO (official secretary), 

SRON, NLR, ISIS BV, VDL ETG, Nedinsco, 

ATG Europe, Hyperion Technologies, and 

Science & Technology. Delft University of 

Tech nology is involved in the cluster as a 

collaborating partner. 

At the end of May 2015, follow-up plans 

were discussed for a concrete collaboration 

between TNO, SRON, and BISME, and a 

Chinese CO 2 satellite mission with Dutch 

S H O R T N E W S 

A cluster of Dutch space companies and institutes 

that focus on the Chinese market – and are seeking 

closer ties – signed a collaboration agreement (INSET) 

on 22 May 2015. 

input is high on the agenda. The mission will 

specifically focus on making an inventory of 

sources and sinks of carbon dioxide (CO 2 ), 

which is an important factor in gaining a 

better understanding of climate change. 

The future CO 2 instrument must distinguish 

itself through a broad field of view. 

5 


Vidi grant for solving the primeval matter puzzle 

SRON researcher Elisa Costantini has received 

a Vidi grant from NWO. Costantini 

and her team will use that money to 

study primeval matter in the interstellar 

medium to throw more light on phenom - 

ena like the birth of stars and the formation 

of planets. 

XX-rays contain a wealth of information about 

this primeval matter. However this information 

has not yet been systematically disclosed with 

the help of the latest tools. Costantini and her 

team will now use high-resolution X-ray spectroscopy 

to systematically study the diffuse 

primeval matter in our Milky Way and other 

nearby galaxies. They will mainly focus on 

sources such as X-ray binaries. These X-rays 

are partly absorbed by the primeval matter 

and partly reflected by it. By analyzing these 

X-rays Costantini and her team can obtain 

information about the composition of the 

matter, for example. Costantini will make 

use of observations from the large space 

tele scopes Chandra (NASA) and XMM- 

Newton, and the Japanese space telescope 

ASTRO-H (now: Hitomi), which was launched 

in Febru ary 2016. 

With the grant, which is worth a maximum of 

800,000 euros, Costantini can set up her own 

new line of research. Costantini: “For a long 

time I’ve been waiting for a chance to solve 

Artist’ s impression of an X-ray binary (NASA/GSFC). 

the primeval matter puzzle. Furthermore, this 

research could in turn be the key to solving 

other problems in astrophysics that can best 

be studied using X-rays. Therefore I cannot 

wait to start. We are going to explore an 

exciting new domain.”

6 


Using small blocks to find big waves 

In 2034, a pair of tiny gold-platinum blocks must give scientists more insight into the evolution of 

the universe and other big questions. They will do this by enabling scientists to analyze gravitational 

waves deep in space. Einstein predicted these waves and their existence was recently confirmed. 

The space probe LISA/Pathfinder is currently on its way to the ultimate test for the eLISA project. 

It is 2034. In a remote part of the solar system several gold-platinum 

blocks just a few centimeters in size float through space. The blocks 

are one million kilometers apart from each other. Nevertheless they 

move through space as if they were synchronized divers in a cosmic 

competition. But then something happens: one of the blocks wobbles 

and the symmetry is briefly broken. A minus point on the jury report 

but actually several months later this imperfection is welcomed with 

huge cheers by scientists on earth. They have then measured the most 

fundamental thing you can possibly measure: a change in the structure 

of space and time. 

Space and time are constant in everyday life. A meter is always just as 

long and a second always just as short. However physicists hold a very 

different view on this. One hundred years ago Albert Einstein discov - 

ered that the amount of matter in an area could influence the structure 

of space and time in that area. Around a heavy object, such as a planet

or star, space-time is curved. As a result of this everything in the vicinity 

is inclined to move towards the object. That is why the moon orbits 

the earth and the earth orbits the sun. Of course we have known 

about this phenomenon far longer under the name of gravity. Einstein, 

how ever, with his general theory of relativity, was the first to describe 

gravity as a curving of space-time. 

Ripple 

His theory gave rise to a hypothesis that was only proved one hundred 

years later. Rapid changes in the quantity of matter at a certain location 

cause space-time to ripple, which is comparable with the ripples 

that arise if you throw a stone in the pond. These space-time ripples 

are known as gravitational waves. They arise, for example, if neutron 

stars or black holes collide with each other. As such extreme phenomena 

provide insights into how gravity works and the formation of 

galaxies, scientists are very eager to study gravitational waves. 

With the small blocks experiment, in which SRON is playing an important 

role, they hope to be able to do that eventually. Whether that will 

actually happen largely depends on the test mission currently in progress. 

On 3 December the European Space Agency ESA launched the 

LISA/Pathfinder probe. In a piece 

According to Einstein of no man’s land in the solar system 

it will be examined whether 

rapid changes in the 

quantity of matter the two gold-platinum blocks on 

should cause ripples board can travel through space 

completely undisturbed. If that is 

in space-time 

the case then it will have been 

proven that the blocks in space can only be disturbed in one way: by 

gravitational waves. That will give the green light for the eLISA mission 

in 2034. 

are looking for gravitational waves with the help of laser beams. 

At these locations two laser beams constantly pass back-and-forth 

through tubes that are perpendicular 

to each other. 

The blocks move in 

exactly the same manner Upon their return the beams 

through space like 

merge. From the light wave 

synchronized divers in pattern of the resulting beam 

you can see whether a gravi - 

a cosmic competition 

tational wave has passed 

through in the intervening time. That is because the detector is set up 

in such a way that the two beams usually cancel each other out. How - 

ever, if a gravitational wave passes through the setup then this briefly 

deforms the setup as a result of which the waves will no longer cancel 

each other out. 

New era 

It took years before gravitational waves were finally unmasked using 

this method. On 11 February 2016 the world of physics threw a party 

when researchers announced that the Ligo detector had measured 

a passing wave on 14 September 2015. The wave had originated 

from two black holes that had merged 1.3 billion years ago. According 

to the scientists involved, the discovery marked a new era in physics 

and astronomy in which measurements of gravitational waves could 

7 


Why will such a delicate experiment be carried out in distant space? 

Although gravitational waves occur everywhere they are very difficult 

to observe. That is first and foremost because gravitational waves in - 

fluence everything in an identical manner. They can temporarily stretch 

a test object but because they stretch your ruler by exactly the same 

amount you will not measure the difference. 

There are many different ways to circumnavigate this problem. The 

Ligo detector in the US and the Virgo detector in Italy, for example, 

Simulation of gravitational waves during a collision between black holes (ESA).

8 


LISA PATHFINDER IS ON ITS WAY TO TEST 

THE TECHNOLOGY FOR GRAVITATIONAL WAVES 

The European space probe LISA Pathfinder (ESA) was success - 

fully launched on 3 December 2015 from the Guiana Space 

Center in Kouro, French Guiana. The space probe was subsequently 

put into orbit around the earth and after that it set 

course for its final orbit around the sun. The probe’s mission is 

to test technology for measuring gravitational waves in space. 

LISA Pathfinder was launched at about 5 a.m. on 3 December 

on a Vega rocket. After two weeks the probe reached the 

highest point of its orbit around the earth and then set course 

to Lagrangian point 1, a relatively stable position at 1.5 million 

kilometers from earth in the direction of the sun. The European 

Space Agency ESA expects that LISA Pathfinder will arrive 

at this position in mid-February 2016. After several tests 

Pathfinder will then start its scientific program at the beginning 

of March and this will last for six months. 

LISA Pathfinder will test the precision technology that is 

needed to measure gravitational waves from space. With this 

the space probe will provide the technological basis for the 

European eLISA mission (ESA, 2034). Dutch engineers and 

scientists are closely involved in international research into 

gravitational waves with experiments on the ground and 

via space probes. Important contributions are being made, 

for example, by SRON, Radboud University, Nikhef, TNO, 

NOVA, University of Twente, University of Amsterdam, Leiden 

University, University of Groningen, and the VU University 

Amsterdam. 

provide answers to big questions about black holes, the big bang, and 

the universe. 

However although it has now been proved that gravitational waves 

can be observed on earth such measurements will never answer all the 

questions. “On earth we can only 

In the future eLISA measure gravitational waves up to 

a few hundred kilometers in size. 

mission four to six 

Interesting objects in space produce 

blocks will float 

far larger waves,” says Gijs Nelemans, 

astrophysicist at Radboud 

in space about one 

million kilometers University in Nijmegen and physicist 

from each other at the Nikhef Institute in Amsterdam. 

Nelemans is one of the au thors of 

the publication that describes the first gravitational wave measurement 

and he is also the leader of the Dutch consortium working on the 

eLISA-project. 

The gold-platinum blocks of the future eLISA mission must, however, 

succeed in exposing the gravitational waves of cosmic mega systems. 

Four to six blocks will float in space at a distance of about one million 

kilometers from each other each protected by a satellite. A third satellite 

will monitor the distance between the blocks using laser beams. 

If a gravitational wave displaces one of the blocks by even by just a 

few billionths of a millimeter compared to the other block than that 

will be registered on earth. 

LISA/Pathfinder 

However the current test mission must first of all be successfully completed. 

The LISA/Pathfinder probe contains two blocks in the same 

satellite that are too close together to unmask gravitational waves. 

The aim of the mission is to demonstrate that the blocks can move 

through space completely undisturbed. 

Scientists will demon- 

Gravitational waves 

arise if neutron stars strate that by using laser beams 

or black holes collide to continuously monitor whether 

the distance between the blocks 

with each other 

changes. “The mission will be 

successful if the baseline measurement is perfect. In other words so 

small as is needed to be able to make gravitational measurements 

with eLISA,” says SRON researcher Martijn Smit, who is working on 

the measurement instruments of both missions.

Nevertheless, there are several factors that can spoil things. “The small 

blocks can only move undisrupted in a single dimension. In the other 

dimensions electric fields must keep them in place. These fields can, 

however, exert a force in the dimension that should not be disrupted,” 

says Smit. “And disruptive electric fields can occur during the readout 

out of the position of the blocks. In addition the particles can become 

electrically charged and the magnetic forces and tidal forces need to 

be allowed for.” 

Accidents can easily happen. What if the baseline measurement is not 

perfect? Will the eLISA mission then be cancelled? “That depends on 

the cause,” says Smit. “For example, if it turns out that the regulation 

of the satellite’s position did not completely work as thought then that 

can still be remedied by working on the codes. Whatever happens, 

everything possible will be done to ensure that eLISA does not experience 

the same shortcomings. So if LISA is not completely successful 

it will still provide very relevant information for eLISA.” 

And even if the eLISA mission proves to be infeasible then the test 

mission will almost certainly not have been a wasted effort. After all, 

space projects often lead to new technology that can also be used on 

earth. Smit: “TNO, for example, has designed two subsystems for 

eLISA in which a mirror can be very accurately moved. That almost 

certainly has other possible applications.” 

YANNICK FRITSCHY 

9 


Dutch contribution 

SRON scientists are excitedly looking forward to the first 

data from the test mission that will start coming in from 

March onwards. In a previous stage, researchers from the 

institute developed test equipment for LISA. SRON is now 

involved in the analysis of the results together with 

researchers from Nikhef, Radboud University, the University 

of Amsterdam, Leiden University, University of Groningen, 

and VU University Amsterdam. 

In addition, SRON is coordinating the Dutch contribution to the 

eLISA mission. TNO developed several systems for that mission. 

One of those systems ensures that the laser beams end up at 

exactly the right place even over a distance of millions of kilometers. 

Besides SRON and TNO, Nikhef, NOVA, and the University 

of Twente are collaborating on the technology for the eLISA 

mission. 

These research institutes are also searching for gravitational waves 

with instruments on earth. Those instruments are the Virgo detector 

in Italy, the BlackGEM telescope in Chile that was designed by 

the Netherlands, and the European Pulsar Timing Array, which 

combines measurements from five large radio telescopes.

Artist impression van PLATO-missie (illustratie: ESA - C.Carreau). 

10 

Distant planets shed light on earth 


Are we alone in the universe? Since the discovery of the first exoplanets 

in 1991 astronomers have feverishly been looking for habitable planets 

outside of our solar system. About 2000 exoplanets have already been 

identified and many thousands more will follow in the coming years. 

So you would expect to find a second earth among all those planets. 

Or is the earth actually quite unique? Recent 

discoveries have revealed that other planetary 

systems can be quite different from our solar 

system. “The statistics so far indicate that the 

most common planet in the universe is two 

to three times as big as earth. Interestingly 

we do not have such a super earth in our 

own solar system,” says Michiel Min, research 

leader of the exoplanets group at SRON. So it 

could well be the case that our solar system 

and the earth are utterly unique. Of course 

that would be a considerable setback in the 

search for life similar to that on earth. 

However, astronomers currently know too 

little about exoplanets to give an answer to 

that. Of the 2000 planets found we often 

know only the period it takes the planet 

to revolve around its star. In some cases 

astro nomers have an indication about the 

size or the mass but that is also not enough 

to state how similar they are to earth. 

Furthermore, the exoplanets found so far 

give a distorted picture. “Some of those 

planets have been found by observing 

wobbles of the star the planets orbit. However 

that phenomenon is only visible in the 

case of heavy planets,” says Min. “Other 

planets have been found because we saw 

them move in front of the star. Using this 

method you mainly find planets located 

close to the star.” 

To resolve the statistical shortcoming more 

exoplanets need to be found and character 

ised. SRON is therefore collaborating in 

two future missions of the European Space 

Agency ESA, in which space telescopes will 

be used to study exoplanets in detail. 

Dips in brightness 

The first is the PLATO mission (Planetary 

Transits and Oscillations of stars), which will 

be launched in 2024. During this mission a 

space probe with 34 telescopes onboard will 

search in the vicinity of about one million 

stars for exoplanets. It will do this by record - 

ing so-called transits. These are the regular 

dips in the brightness of a star, which can

indicate that a planet is moving in front of 

the star. 

Many exoplanets have already been discov - 

ered using this transit method, for example 

by the space telescope Kepler. However, the 

PLATO mission will go a step further. “Kepler 

can only map a very small piece of the sky. 

PLATO will examine almost the entire sky so 

that all bright stars can be studied at the 

same time,” says Min. “Furthermore PLATO 

will not just measure for a few months but 

for several years. That will make it possible 

to find exoplanets that take longer to orbit 

around their star. Such as the earth which 

takes one year to orbit the sun.” 

SRON is expected to contribute to the PLATO 

mission by providing test facilities. Min: “The 

34 telescope cameras must all be tested at 

extremely low temperatures for factors such 

as stability and precision. We want to carry 

out some of these tests at the institute in 

Groningen.” 

Eventually astronomers will collate all of the 

values measured in a catalogue of thousands 

of exoplanets. They will then be able to use 

this to determine which exoplanets merit fur - 

ther research. The next step will be to es tab - 

lish the exact composition of these plan ets’ 

atmospheres. The ARIEL mission (Atmo spheric 

Remote-Sensing Infrared Exoplanet Large 

sur vey) has been proposed for that. In the 

first half of 2017 the ESA will have to make a 

choice between this and two other proposed 

missions. If the ARIEL mission is selected then 

it will be started in about 2025. 

Hot Jupiters and super earths 

“I think the time is ripe for a mission like 

ARIEL,” says Min. “There are already a lot of 

missions to identify exoplanets but few of the 

planets found are being characterised. This 

requires telescopes that can remain stable 

over a long period of time like the James 

Webb Space Telescope that will become oper - 

ational in 2018. However exoplanets will be 

Proposal for the ARIEL telescope (ESA). 

just one of the things it observes. Hopefully 

ARIEL will get the go-ahead and observe only 

exoplanets.” 

In the case of the ARIEL mission a telescope 

onboard a space probe will carry out mea - 

surements on about 500 exoplanets over a 

period of 3.5 years. Those will mainly be the 

There are many missions 

to identify exoplanets 

but few exoplanets are 

being characterised 

‘hot Jupiters’ and ‘super earths’: large planets 

with a temperature of several hundred 

degrees Celsius. “Only such planets have 

atmospheres thick enough to be measured,” 

says Min. If the ARIEL mission goes ahead 

and it uses European detectors then engineers 

from SRON will contribute by developing the 

readout electronics. SRON scientists are also 

eagerly looking forward to the moment that 

the results from this and the PLATO mission 

can be analysed. Min: “We still know little 

about the cloud formation on exoplanets. 

In addition, the measurements will give insight 

into the formation of planets. More data 

are needed to be able to statistically demonstrate 

where and how planets are formed in 

general.” 

Extraterrestrial life 

A better understanding of the formation and 

evolution of planets should also lead to an 

answer to the ultimate question concerning 

extraterrestrial life. According to Min, how - 

ever, the PLATO and ARIEL missions will get 

nowhere near to answering these questions. 

“We cannot characterise planets as small as 

earth yet. We can characterise super earths 

but only if they are located quite close to the 

star. As a result of that they are too warm to 

support life.” 

Min is cautiously optimistic about the chance 

that we are not alone. “Up until now everything 

that is physically possible also occurs in 

the universe. Billions of earth-like planets are 

therefore expected to exist. Then we need to 

ask: Is the chance of life evolving on such a 

planet greater than one in a billion? We don’t 

know and we are currently doing the statistics 

on a sample of one. That number needs to be 

bigger.” 

The question about life will therefore remain 

unanswered for the time being. Hopefully 

future missions will be able to demonstrate 

whether our solar system is commonplace or 

completely unique. 

YANNICK FRITSCHY 

11 

SRON Spectrum

How do black holes grow and how do they influence 

12 


the galaxies they are a part of? How does matter 

conglomerate into galaxies? Where do the 

mysterious X-rays in clusters of galaxies come from? 

The X-ray telescopes ASTRO-H (now: Hitomi, 2016) 

and ATHENA (2028) can answer these and other 

questions about the ‘hot’ and energy-rich universe. 

SEARCHING 

FOR ANSWERS 

IN THE HOT UNIVERSE 

Artist’s impression of ATHENA (ESA). 

The most extreme objects in the universe emit 

X-rays. Astronomers need space instruments 

in space to study those hot and energy-rich 

phenomena, because high-energy X-rays cannot 

penetrate the earth’s atmosphere. Therefore 

they make use of X-ray telescopes like 

XMM-Newton (ESA) and Chandra (NASA) and 

from this year onwards ASTRO-H (now called 

Hitomi, JAXA) – the launch of this Japanese 

telescope took place in February 2016. How - 

ever to look far deeper and in greater detail 

into black holes and distant clusters of galaxies 

a next generation of X-ray instruments 

is needed. The European Space Agency ESA 

has therefore selected ATHENA (Advanced 

Telescope for High Energy Astrophysics) as the 

second large space mission for the following 

decade. The X-ray telescope will be fitted with 

two instruments: a camera/spectrometer 

(X-ray Integral Field Unit, X-IFU) and a wideangle 

space camera (Wide Field Imager, WFI). 

Detectors 

With a weight of about 5000 kg, a length of 

about 14 meters, and an X-ray lens with a 

diameter of three meters ATHENA will be the 

largest X-ray telescope ever. That is good 

news for Dutch space research: SRON will 

pro vide the ultrasensitive detectors for the 

camera/spectrometer X-IFU and thanks to this 

contribution SRON researchers will be given 

guaranteed observation time on the advanced 

telescope. They are looking forward with considerable 

interest to the answers that ATHENA 

It is a completely natural 

process and it does not 

involve any magical things 

or exotic particles 

will give to three important scientific questions: 

what is the composition of the elusive 

hot matter in clusters of galaxies, how does 

matter conglomerate into galaxies and clus-

ters of galaxies, and how do black holes grow 

and influence their surroundings? However, 

they will need to be patient because the 

launch of the space observatory is planned for 

2028. 

Matryoshka dolls 

One of the researchers is SRON astronomer 

Peter Jonker. Last year Jonker and his colleagues 

caught a supermassive black hole 

tearing a star apart. The black hole was quite 

bright in the radio spectrum – there was 

already an accretion disk with the flow of 

matter moving towards the black hole – 

but not so bright in the X-ray spectrum. 

“Until a star passed that was being torn 

apart,” explains Jonker. “Due to the new 

flow of matter into the black hole, it entered 

an entirely different mode.” 

After this powerful injection of gas, Peter 

Jonker and his team observed a strong in - 

crease in X-rays and visible light, while the 

radio emission became weaker. The radio 

emission most likely originates from a jet, 

a fast gas flow emitted by the black hole. 

This fits exactly in the pattern that is observed 

in much smaller stellar black holes. In general, 

these are quiet and occasionally experience 

an eruption during which they first become 

brighter in the X-ray and radio spectra until 

the flow of matter is so large that the X-ray 

spectrum becomes dimmer, whereas the radio 

spectrum decreases by factor of more than 50. 

Jonker: “And that pattern was also found for 

a supermassive black hole. We call this the 

Matryoshka principle, which predicts that all 

compact objects in universe that attract 

matter behave the same with a correction 

based on their mass.” 

Medium-sized black holes 

To gain a better understanding of this pro - 

cess es Jonker wants to use ATHENA to start 

hunting for black holes that are not extremely 

heavy but are also not stellar, so-called 

medium -sized black holes. Up until now the 

masses of the candidate medium-sized black 

holes are all based on rough estimates. Only 

a handful of good candidates are known 

but these are located so far away that as - 

tronomers cannot determine how large the 

orbits of the stars around the black hole are 

and therefore cannot calculate the mass of 

the black hole. 

If we can find a white 

dwarf that is being torn 

apart then the perpetrator 

has to be a medium-sized 

black hole 

Jonker: “Medium-sized black holes (a thousand 

to ten thousand solar masses) can also 

tear stars apart but that only happens if a star 

comes relatively near. And then the time scales 

are much shorter, so you have little time to 

make your observation.” Jonker is mainly interested 

in white dwarfs that are engulfed by 

such medium-size black holes. “Supermassive 

black holes can also do that but that only 

occurs after such a star has passed the observation 

horizon. Therefore we do not see it.” 

If we can find a white dwarf that is being 

torn apart then the perpetrator must be a 

medium-sized black hole. As soon as a radio 

or optical telescope has observed such an 

event we can then immediately observe it in 

the X-ray spectrum using ATHENA. Jonker 

also hopes that the intended wide-angle 

▶ 

13 


From top to bottom: Hot gas cloud as a consequence 

of the Tycho supernova (NASA/CXC/SAO); 

Black hole (NASA); supermassive black hole blows 

bubbles in the hot gas of the Perseus cluster 

(NASA/CXC/SAO/E. Bulbul, et al.).

14 


camera (40x40 arc minutes imaging field) can Sulfur 

find many medium-sized black holes. “As Using ASTRO-H/Hitomi, Kaastra and other 

soon as ATHENA finds sources that suddenly SRON researchers will, amongst other things, 

flare up we will immediately send a message test whether the explanation that they recently 

found for elusive X-rays in clusters of 

so that other telescopes can observe this in 

the visible light and radio spectra.” 

galaxies is correct. Up until now some astronomers 

have ascribed this radiation to a 

ASTRO-H/Hitomi 

hypothetical particle, the sterile neutrino, 

For SRON astronomer Jelle Kaastra another which is possibly the source of dark matter. 

exciting X-ray mission has his attention first. However, Kaastra and his colleagues discov - 

That is the Japanese X-ray telescope ASTRO-H, ered that the X-rays could arise if cold hydrogen 

gas collides with hot sulfur ions. 

now renamed Hitomi, which was launched 

from the Tanegashima Space Center in Febru - 

ary. SRON has collaborated on the filter wheel Kaastra: “Those clusters of galaxies contain 

on ASTRO-H/Hitomi, which slightly dims a combination of lots of cold and warm gas. 

sources that are too bright. Some binary stars, If these mix then you can obtain those tran - 

in particular, are so bright that the detector sitions and nobody had realized that up until 

be comes saturated. The filter discards ninety now. It is a completely natural process and it 

per cent of the photons but still enables you to does not involve any magical things or exotic 

particles. As the signal 

is incredibly weak 

and there is a wide 

range of spectral lines 

in the vicinity, we initially 

had some 

doubts about it. Now 

we have elaborated 

our model and it 

corre sponds exactly.” 

ASTRO-H/Hitomi will 

provide high-resolution 

spectra for the 

high energies and it 

will make high-reso lu - 

tion spectra of elongated 

sources in 

ASTRO-H- satellites ready for launch at the Tanegashima Space Center (JAXA). 

space. “Up until now 

obtain a good spectrum. In collaboration with we did that using XMM with gratings but 

Photonis, SRON also supplied the calibration that only works well for point sources. For 

source that determines whether the energy elongated sources in space the signal is 

scale of the detector is still properly calibrated. spread out too much. ASTRO-H/Hitomi can, 

however, make these spectra for the first 

time.” 

Harvest 

From ASTRO-H/Hitomi to ATHENA is the next 

big step. ATHENA will have a far greater field 

of view and will be able to make far more 

detailed observations. 

“We call this the 

Matryoshka principle, 

which predicts that all 

compact objects in 

universe that attract 

matter behave the same” 

Hitomi has a resolving power of one arc 

minute but the discriminatory power of 

ATHENA will be twenty times better. Kaastra: 

“ATHENA will have a far larger effective surface 

and will therefore be far more sensitive, 

also compared with our own RGS spectrometer 

on the space telescope XMM-Newton. 

That covers one- hundred square centimeters, 

whereas with ATHENA that will be two square 

meters, which will allow the telescope to capture 

more light by a factor of two hundred.” 

ATHENA will therefore be able to observe 

extragalactic sources in the far red shift, 

back to the time in which they arose, at the 

‘boundary’ of the universe. 

Meanwhile however, Jonker and Kaastra will 

use other instruments as well. XMM-Newton 

and Chandra have about another ten years of 

service. And with Hitomi the first data will be 

harvested in the coming years. 

MARIEKE BAAN

Photo: NASA. 

In our atmosphere minuscule dust and 

fluid particles that influence our climate 

are floating around. Examples are sea salt 

or soot particles from traffic. Yet how 

these aerosols contribute to global 

warming is still a mystery. Where exactly 

are aerosols emitted? Are they harmful 

for us? NASA’s climate satellite PACE 

will search for answers to these and 

other questions, possibly with the help 

of a Dutch instrument. 

Aerosols: missing link in climate research 

15 


Global warming is one of the biggest challenges of this age. Models, 

however, differ considerably with respect to the speed and extent to 

which the climate is warming up. One of the reasons for this uncertainty 

is that we still do not know enough about the mechanisms 

under lying climate change. The influence of aerosols is one of the most 

important climate factors that we still know relatively little about. 

Aerosols are minuscule solid or liquid particles that float around in the 

atmosphere. They can come from natural sources, such as ash from 

volcanic eruptions, sand from the Sahara or sea salt from the oceans. 

However humans also emit large quantities of aerosols with the combustion 

of fossil fuels and wood. Dependent on their composition, 

the particles can exert either a warming up or cooling down effect on 

the climate. They influence the temperature through radiation effects 

and cloud formation. Some types of particles cool the climate by acting 

as tiny mirrors that reflect sunlight directly into space. Other types, how - 

ever, can absorb solar radiation or heat emitted by the earth and then 

emit this again as result of which the greenhouse effect is en hanced 

and the atmosphere warms up. Aerosols also play a role in the formation 

of clouds because water condenses on small aerosol particles and 

consequently forms clouds. In turn these clouds exert an influence on 

the climate system. 

There are many different types of aerosol particles and their interactions 

with the climate are complex. So at present we do not know how 

aerosols contribute to changes in our climate. We are not even entirely 

sure whether on balance aerosols enhance or mitigate global warming. 

With our current level of knowledge, the uncertainty regarding the 

worldwide effect of aerosols is just as big a factor as the total effect of 

the greenhouse gas carbon dioxide. SRON program leader Avri Selig: 

“To find out how aerosols influence the climate we must know exactly 

how many particles are 

“We are not even entirely 

located where in the atmo - 

sure whether on balance 

sphere, whether these 

aerosols enhance or mitigate 

particles absorb or reflect 

global warming...“ 

radiation, and what the 

composition of these particles is. Furthermore, if we know the composition 

of the particles we can determine whether they are harmful for 

public health and how harmful they are. So far this knowledge is not 

available on a large scale.” 

The role of satellites 

Measurements of aerosol properties on a global scale are needed to 

understand the influence of aerosols on the climate and air quality. 

Such measurements can only be obtained with the help of satellites.

16 


For the characterization of aerosols it is important that a satellite instrument 

measures both the intensity and polarization of the light reflected 

by the earth’s atmosphere. Up until now only one such instrument has 

been launched: the French POLDER instrument onboard the PARASOL 

satellite. Its successor, the 3MI instrument of ESA on the MetOp-SG 

satellite, is a similar measurement instrument that is expected to be 

operational from 2021 onwards. The aerosol measurements from these 

being developed by the NASA Goddard Space Flight Center, and a 

polarimeter. Due to its technical and scientific specifications SPEX is 

NASA’s preferred choice for a polarimeter. The two measurement 

instruments complement each other: measurements from the polari - 

meter help to correct ocean measurements and the OCI instrument 

measures certain properties of clouds and aerosols. Together these 

instruments will provide data that are important for multidisciplinary 

satellite missions will mainly provide information about the quantity 

climate research. 

“There are many 

and size of the particles but will not reveal enough about the extent 

different types of 

to which the particles absorb or reflect light and almost nothing about 

If efforts to obtain sufficient national 

aerosol particles and 

their chemical composition. 

funding are successful then NASA 

their interactions 

will definitely select SPEX for PACE. 

A major step forward in aerosol research requires a new instrument 

that is far more accurate. SRON already has a prototype for that in - 

with the climate are 

complex“ 

SRON would then become responsible 

for the construction of the instrument 

strument: SPEX. Otto Hasekamp, Principal Investigator for the SPEX 

instrument: “Thanks to an entirely new measurement principle, SPEX 

mea sures more accurately than its predecessors by more than a factor 

of ten. Therefore with SPEX we can determine the extent to which 

aerosols absorb and scatter light. We can also determine the chemical 

composition of aerosols. For example, 

the instrument will help us to distinguish 

sea salt from harmful soot.” 

and the processing of the data. Together with Dutch parties, 

SRON would then ensure the integration of the different subsystems 

and also carry out the various tests. Furthermore, SRON will produce 

part of the flight electronics, will perform the calibration, and will deliver 

the associated software. After the launch, SRON scientists will 

derive aerosol properties from the 

spectro-polarimeter data. The importance 

of SPEX for NASA is ap - 

parent from the major contribution 

The technology behind SPEX has already 

been successfully used for local groundbased 

that NASA wants to make to the 

SPEX instrument. 

aerosol measurements at the 

Dutch atmospheric measurement mast 

in Cabauw (the CESAR Observatory). 

Better climate predictions 

The measurement results from 

The SPEX technology was also used in 

PACE/SPEX will help climate researchers 

to gain a better under- 

Sea salt, dust, and volcanic ash are aerosols 

Leiden University’s citizen science project 

from natural sources (Katherine Mann). 

iSPEX, which won the Academische jaarprijs 

in 2012. Furthermore, SRON has constructed an airborne version of 

the SPEX instrument prototype for a flight under the NASA research aircraft 

ER-2, which performs measurements at an altitude of 21 kilometers. 

This instrument, called SPEX Airborne, first flew in February 2016. 

standing of the role of aerosols in 

the earth’s climate and to quantify this. That will lead to better climate 

predictions, which in turn will help to determine the climate policy. For 

example, the results could contribute to a report from the Intergovernmental 

Panel on Climate Change (IPCC), which is published once every 

five to six years. In addition, with the arrival of PACE/SPEX, scientists 

PACE mission 

As SPEX is so accurate, NASA would like the instrument to fly onboard 

its climate satellite PACE (Pre-Aerosols, Clouds and ocean Ecosystems), 

will be able to accurately determine the origin of air pollution. This information 

is extremely valuable for government bodies when they take 

measures to improve air quality. 

the launch of which is planned for 2022. The PACE satellite will have 

two instruments onboard: the Ocean Color Instrument (OCI), which is 

EVELINE VAN DER LINDEN

THE EXPERTISE TRIANGLE / SPACE INSTRUMENTS 

SPEX airborne ready 

for scientific flights 

The SPEX technology has been designed to investigate aerosols 

(small particles) in the atmosphere from space. A prototype 

– SPEX airborne – has been converted to fly onboard a NASA 

research plane at an altitude of 21 kilometers. A team of SRON 

engineers has assembled this instrument over the past months 

and prepared it for the harsh conditions found at that altitude. 

SPEX airborne has successfully completed more than five flight 

hours. 

17 


The ER-2, the NASA research plane that carries SPEX airborne (NASA). 

EEach component looks the part. All of the components have been 

manufactured from aluminum and have a golden glow. Bolts have 

been placed with surgical precision at perfectly regular distance from 

each other. It is clear that the instrument has been produced by specia l - 

ists. SPEX airborne is ready for its first flight in Palmdale, Cali for nia. The 

SPEX instrument will be installed in the wing compartment of a NASA 

research plane (the ER-2). The instrument has been thoroughly tested 

over the past few months. In addition, SPEX airborne has successfully 

completed an extensive set of electrical tests. 

Extreme conditions 

At an altitude of 21 km it is just as cold as in the Antarctic winter and 

the pressure there is comparable with that of a vacuum. Via observation 

holes, SPEX airborne is in 

“At an altitude of 21 km 

direct contact with this outside 

air, as a window would 

it is just as cold as in 

the Antarctic winter and disrupt the incoming light. 

the pressure there is The instrument must therefore 

be able to carry out 

comparable with that 

measurements under these 

of a vacuum” 

conditions. Many standard 

electronic components are not suitable for this due to problems with 

the dissipation of heat as result of which electronics can burn out. 

SRON researchers therefore designed and built special components and 

systems, or purchased these. For the required accuracy of SPEX airborne 

it is vitally important that the optical system – the heart of SPEX 

airborne – does not vary in temperature too much. Heating elements 

ensure that the optics of SPEX and the associated camera remain at 

room temperature with a deviation of less than 0.1 °C even though the 

outside temperature is -55°C. 

T H E E X P E R T I S E T R I A N G L E 

SRON develops, builds and uses instruments that 

enable scientific breakthroughs in space research. 

This section in the Spectrum newsletter features 

a different aspect of SRON’s expertise triangle 

each time: 

▶ Science covers astrophysical and atmospheric research and 

spectroscopy. 

▶ Enabling Technology develops detectors, readout electronics, 

micro- mechanical systems in very cold conditions, lithography 

facilities, and cleanrooms. 

▶ Space Instruments concerns the system knowledge and the 

design, development, construction, and approval of flight 

instrumentation in international consortia.

18 


Photo top right: Engineers from SRON 

and NASA carry out the last tests 

at NASA’s Armstrong Flight Research 

Center in Palmdale, California. 

Top and right: SPEX airborne in 

the wing compartment of the ER-2 

(view from below and from the side). 

From Mars to Earth 

SPEX was originally designed for a Mars mission. The sensitivity of the 

SPEX prototype, however, far exceeded all expectations during the 

tests in 2013 and 2014. SPEX was found to measure five times more 

accurately than the purpose for which the instrument had been designed. 

As a result of this SPEX immediately became interesting to use 

for measurements of fine particles (aerosols) and clouds in the earth’s 

atmosphere. SRON scientist Otto Hasekamp is leading the scientific 

studies that will be done using the data from SPEX airborne: “We 

already had a long-term collaboration with researchers from NASA in 

the area of aerosols, clouds, and the interactions between these. 

What does SPEX measure? 

SPEX measures the sunlight that is scattered by dust and 

other small particles in the atmosphere, so-called aerosols. 

The instruments can recognize these particles from their 

optical and micro-physical properties by measuring the 

degree of polarization under different angles. Aerosols have 

a lot of impact on the air quality and the climate. With the 

help of SPEX we can come a step closer to solving many of 

the unanswered questions about climate and air quality. 

From this collaboration the plan arose to place the SPEX prototype on 

an aircraft for a series of measurement campaigns. The ER-2 aircraft is 

a former spy plane and flies so high that almost the entire atmosphere 

lies beneath you. It is therefore almost like a satellite.” 

Heavy and independent 

An awful lot had to be done to make the SPEX prototype suitable for 

the research plane. As explained earlier, the instrument has to function 

well under the extreme conditions at an altitude of 21 km. However 

that is not everything. The system must be able to work entirely independently 

because there is nobody who can operate the instrument 

during the flight. The pilot can only switch the instrument on and off. 

Controlling the instrument from the ground is not possible either. 

To achieve this, not only the prototype and the camera are needed, but 

an Instrument Control Unit (ICU) and Instrument Power Unit (IPU) as 

well. The ICU is an onboard computer that ensures the control and 

readout of the camera, the storage of the raw data, the collection of 

relevant flight data, and the calculation of the temperature regulation. 

In a nutshell it keeps an eye on the instrument’s health. The IPU en - 

sures that each component receives enough electricity so that possible 

electrical problems in the instrument cannot damage the plane. An 

aluminum shield with small observation holes covers the instrument 

to make it easier to keep the temperature stable. 

SPEX airborne has been developed from the original Mars model by 

SRON engineers from Utrecht and Groningen. Hasekamp: “What 

makes this project so special is that SRON has not only developed the 

entire airborne system 

“SPEX airborne is hopefully and made nearly all of 

a dress rehearsal for larger the components, but the 

missions, such as the NASA/ instrument has been 

PACE mission” 

calibrated by our instrument 

scientists, and our 

scientists will shortly carry out the data analysis as well. The entire 

cycle therefore bears the SRON mark.” 

Deliberately making mistakes 

The instrument is tested by subjecting it to about one hundred tests 

in which simulations of various errors are performed. Examples are 

variable temperatures, currents or voltages that are too high or too

low, or a component in the system that does not respond or responds 

in a strange manner. In some cases the pilot can restart the system 

but after three restarts, the system switches itself off. Even that is 

simu lat ed in the testing phase with a box that simulates the on, off, 

and restart buttons of the pilot. The aim is to anticipate as many errors 

as possible so that the system can continue to function during flight. 

Instrument scientist 

“The instrument’s accuracy Martijn Smit was involved 

ensures that you can 

in testing SPEX airborne. 

distinguish between 

different types of aerosols, “Many of these tests 

for example desert dust, work automatically but 

generating errors can also 

sulfate, and soot” 

be very time-consuming,” 

explains Smit. “Although all of the components are individually tested, 

new problems always emerge as soon as the components become 

part of a larger system. Most of the problems are small in nature and 

quickly solved. A bug in the software, a small design error in an electronic 

circuit, or a component that proves to be unreliable. But a few 

persistent problems always take up the most time. Nevertheless we 

ultimately still manage to find a solution.” 

Successful test campaign 

At the end of January 2016 NASA mounted the SPEX instrument on 

the ER-2. Four SRON engineers and an instrument scientist were 

present in Palmdale to assemble the individual components and to 

perform tests with a special simulator that simulated all electronic 

connections with the plane. The first test flights with the SPEX instrument 

took place immediately afterwards. These enabled the team 

to fine-tune the instrument. During the third flight SPEX airborne 

flew together with the AirMSPI instrument of the Jet Propulsion Lab, 

a similar type of measuring instrument. During this flight SPEX airborne 

performed as expected. Now an exciting period follows in 

which scientists will analyze the data. This will include, for example, 

a comparison of the data from AirMSPI with that from SPEX airborne. 

The initial results look highly promising. 

From airborne to space 

The outcomes of the scientific measurement campaigns that will be 

obtained during these flights will hopefully provide us with a better 

understanding of the earth’s climate and air quality. Hasekamp: 

Photo top: SPEX airborne on 

the integration table in SRON’s 

cleanroom. The optical module 

with nine observation holes is 

in the semicircular part. 

Photo left: SRON instrument 

scientists measure the currents 

through the electrical connec - 

tions in the Instrument Power 

Unit, which has just been 

attached. 

“The instrument’s accuracy ensures that you can distinguish between 

different types of aerosols, for example desert dust, sulfate, and soot. 

Furthermore you can determine whether the aerosols mainly reflect 

radiation (cooling effect) or also absorb it (warming effect). That is very 

important information for understanding the effect of aerosols on the 

climate. By combining SPEX airborne with other instruments that measure 

from ER-2, we can also find out more about the effect of aerosols 

on cloud formation. Furthermore, the results from SPEX airborne will 

provide us with a lot of useful information about future aerosol space 

missions. The SPEX airborne mission is hopefully a dress rehearsal for 

larger missions, such as PACE, which will perform similar measurements 

from space.” 

EVELINE VAN DER LINDEN 

19 

SRON Spectrum

Wouter Laauwen in his ’big red’, the red jacket with the insulation and weight of a double duvet. 

20 


Wouter blogs... 

From the South Pole to the edge of the universe… 

At the end of 2015, Wouter Laauwen blogged about his work for the balloon mission STO2. The NASA mission was due to 

circle above the South Pole from the start of January onwards. Aim? To find out more about how stars and planets are born 

in molecular clouds from the edge of space. The launch has now been postponed until the end of 2016/2017. Nevertheless, 

Laauwen’s experiences as a pole traveller are still worth reading...

2 November 2015, Los Angeles: 

How it started 

A 

Actually my mission to the South Pole started 

a long time ago. Snow, ice, and cold have 

fascinated me since I was very young. As a 

small boy I read about the polar explorations 

of Willem Barentsz, Roald Amundsen, and 

Ernest Shackleton, with glowing cheeks and 

I devour ed the books of Jack London (White 

Fang). Later series such as Game of Thrones 

were added to this list. As an engineer at 

SRON I therefore sometimes dreamed about 

scientific trips to the polar regions. To places 

where almost nobody comes, with endless 

snow and ice, and an all-powerful nature. If 

only I could get the chance. Wow. 

STO2 on time. We offered to develop a 

backup for it here in the Netherlands to 

ensure that the mission could go ahead. In 

just four weeks we managed to develop a 

detector block for four pixels, to coat lenses 

for the right frequencies, and select detectors 

for the four positions. Our developmental 

sprint resulted in us having a working backup 

for the detectors that we could show at an 

interim project review of NASA. This proved 

to be crucial: ultimately the SRON detectors 

were selected for STO2. 

5 November 2015, Christchurch: 

package one delivered! 

On the way to Antarctica my favorite guessing 

game became: Who else is going to Antarctica? 

That’s not easy, however, because how 

I need you to be the 2nd person 

to be in the Antarctic. 

Are you willing? 

can you tell? Clothes? Fitness? After all, we 

have all completed the same approval program. 

Meanwhile I am reading The Martian 

21 


So when SRON project leader Jian-Rong Gao 

asked me whether I could help as a systems 

engineer with STO2 it was a dream come 

true. On 15 April 2015 the redeeming email 

eventually came from Gao. It was a bit James 

Bond-like and consisted of three short sen - 

tences: I need you to be the 2nd person to be 

in the Antarctic. Are you willing? If yes, I need 

to check with Pieter - Gao. My wife and son 

were both excited (“We are coming with you 

to America.”) whereas my daughter was in 

tears (“Papa is going away for a very long 

time.”). 

At LA International Airport the inevitable farewell 

came. You cuddle your wife and children 

once more, and a tiny bit of doubt creeps into 

by Andy Weir, which has now been filmed 

with Matt Damon in the leading role. 

To places where almost nobody 

comes, with endless snow and 

ice and an all-powerful nature. 

Wow 

Meanwhile on the other side of the pond the 

process was encountering problems. In the 

spring it became clear that the American Jet 

Propulsion Laboratory (JPL) was having difficulty 

in delivering the infrared detectors for 

your mind. So far away and for such a long 

time. What if something happens? And of 

course tears flow. And then all of a sudden 

they have passed through security and are on 

their way to the next step of their own small 

adventure. Back home without a husband 

and father. I return to the hotel to write my 

first blog in the lobby and to wait for my own 

flight to Sydney. 

An inspiring book if you need to write a blog 

on Antarctica. I had already planned to start 

one of my blogs with the words: “Captain’s 

log, star date 41153.7, our destination is 

McMurdo...” Now I just need to add an intro: 

“Log entry: Sol 7. Okay, I had a good night’s 

sleep and things don’t seem as hopeless as 

they did yesterday...” My plane to Sydney 

turns out to be an enormous Airbus A380. 

The video channel is playing Interstellar.

22 


STO2 loses the race against the clock at the South Pole 

The balloon mission STO2 did not take off from the South Pole. The balloon, 

which is equipped with Dutch detectors, was meant to make a circular flight above 

Antarctica at the start of this year at an altitude of 40 km to make observations 

of the universe. However due to bad weather the balloon could not be launched 

on time to still benefit enough from the circular polar wind. The mission has, 

in principle, been deferred by NASA to the end of 2016/start of 2017. 

Ultimately the weather gods proved unfavor - weather has been so unfavorable,” says project 

leader Jian Rong Gao (SRON/Delft Uni- 

able towards STO2. Until 21 January there 

was still the hope that the balloon could follow 

the GRIPS mission and be launched on test it was all systems go and the detectors 

versity of Technology). “After the hanging 

time. But a persistent strong wind eventually were functioning superbly. All of the teams 

made that impossible. Launching the balloon did exceptionally good work. But the weather 

now would mean that the balloon would not is one thing you cannot influence. Fortunate - 

be able to make a circular flight and would ly, NASA plans to make a new attempt at the 

probably end up in the sea instead of landing 

on the South Pole. 

end of this year or the start of next year.” 

Astronomers could have used STO2 to measure 

atomic oxygen for the first time from 

“A real shame. And also terribly bad luck 

because it is the first time in 20 years that the the edge of space. With those measurements 

they can directly detect the incubators 

of new stars: the oxygen line tells us which 

areas in the gas clouds between stars have 

been warmed up by recently formed stars. 

STO2 (NASA) has extremely sensitive detectors 

for three different frequencies (1.4, 1.9, 

and 4.7 terahertz). These detectors have 

been built by SRON and Delft University of 

Technology. SRON and Delft University of 

Technology have also developed a local oscillator 

(4.7 terhertz) in collaboration with MIT. 

This is essential for measuring the signal 

from space with respect to the frequency 

(position) and spectral information. 

The University of Arizona is leading the 

scientific aspects of the project, which is 

being funded by NASA, NWO, SRON, and 

the province of Groningen. 

A captivating and moving story, but not such 

a fine film if you have just taken leave of your 

wife and children for a long period of time. 

It has the same effect as a strong Fisherman’s 

Friend… tears in the eyes… 

9 November 2015, Antarctica: 

beautiful but merciless! 

On 7 November, at the Clothing Distribution 

Centre in Christchurch, it becomes serious. 

About 40 people have assembled in the 

briefing room. A video gives us an idea as to 

what we can expect on McMurdo. The main 

message: Antarctica is beautiful but merciless. 

After some checks – flu jab...check!, 

computer security certificate...check!, were 

are allowed to go to the dressing room. 

After a few days I find a routine 

but not one I can get use to, as 

Antarctica is too grand for that 

Here rows of orange bags have been put out 

that contain our Extreme Weather Clothing. 

We then somewhat awkwardly put on overalls, 

hats, thick jackets, and bunny boots:

shoe size Pipo de Clown. Air insulates really 

well, so the idea is to capture as much of it as 

possible in the clothing. And indeed we all 

look like Michelin men but then red ones. 

In the transport plane to McMurdo, a C17, 

I choose a jump seat opposite a pallet with oil 

drums. Even with my legs stretched out I do 

not touch them. Fantastic, so much space. 

As the plane taxis the pallets shift backwards 

and forwards on the roller track. Is that meant 

to happen? 

And then the engines go full throttle and we 

journey on a road across the ice it is surpri - 

singly bumpy. McMurdo turns out to be not 

particularly beautiful… but definitely special. 

It is far more than just 

the landscape: it is the light, 

the cold, the wind, and 

the unbelievable distances 

In a room we are given another briefing, this 

time about the dos and especially about the 

don’ts on Antarctica. The entire continent is 

protected by a series of treaties and one of 

After dinner I go for a short walk. With the 

wind from behind and the sun in my face it 

does not feel too cold. What a fantastic view 

across the Ross Sea. On the other side gigantic 

glaciers flow into the sea. The air is so clear 

and dry that you can easily see over a distance 

of 100 km. That is one of the reasons why 

we are here. However this makes estimating 

distances really difficult and it distorts your 

observation of the area. On the way back the 

wind picks up and then I suddenly realize 

what a difference a jacket can make. With 

my head buried inside the hood of my jacket 

23 


take off. What a unique experience. After 

about five hours in the air the pilot brings the 

plane down softly on the ice. Once we have 

stopped, the large tailgate at the back of the 

plane opens. Outside an entirely new world 

beckons: white, clear, bright light, mountains, 

a smoking volcano, and a large red lorry with 

a people carrier that will bring us to McMurdo. 

We are on Antarctica! 


First warning 

In the bus after the landing I notice that for a 

the most important is that it must remain undamaged. 

Everything that comes in must also 

go out again. Even spilling coffee on the snow 

must be reported as an incident and neatly 

cleaned up. This will ensure that the unspoiled 

character of the area will be con served for 

the future. I share my room with John, an 

American colleague from the Jet Propulsion 

Laboratory. The idea of sharing a room for 

5 weeks takes a bit of getting used to. 

The heater is on 10 and the sun shines into 

the bedroom. Yet outside it is -20˚C: long 

underwear weather. 

I keep walking. My cheeks quickly start sting - 

ing and then they go numb, which is not 

good. Fortunately I only have a short way to 

go but I got the message: at -20˚C things can 

go wrong quickly. Next time I must take the 

balaclava in my pocket. But what a fantastic 

landscape. 

Inside our hanger is the balloon gondola. It is 

almost ready for use. We are going to incorporate 

our instrument in the cryostat, a sort 

of large thermos flask filled with liquid helium 

that cools the entire instrument to about

24 


- 270°C, or 4 Kelvin, 4° above absolute zero. 

Although everything in more primitive you 

can easily forget where you are because the 

lab has no windows. As soon as the door 

opens it becomes clear again, I really am on 

Antarctica. 

It is far more than just the landscape: it is the 

light, the cold, the wind, and the unbelievable 

distances, the knowledge that the nearest 

place with normal facilities is a 4000 km flight 

away. No telephone, scarcely any Internet 

(almost everything is blocked or highly restrict - 


Scott’s hut... 

Another week has passed in McMurdo. Some 

things have become normal: sharing my room, 

three warm meals per day, and long woolen 

underwear. Other things remain special: the 

fantastic landscape, the weather that can 

change from pleasant to extreme in five min - 

utes if the wind picks up, and the sun that 

shines from the south at 12:30 at night. It’s 

still strange that when you leave the pub at 

night, you need to put on sunglasses. 

I sometimes still wake up at night with a 

making progress but as we are working with 

a unique instrument we also encounter unique 

problems. In combination with limited labora - 

tory equipment and the fact that the nearest 

The biggest problem is ESD, 

ElectroStatic Discharge 

shops are 4000 km away, that some times 

demands a healthy dose of creativity. And 

that is why we are here. 

My visit to the so-called OB tube, an observation 

post in the ice, is memorable. Or to be 

ed to keep the bandwidth available for the 

scientific projects), no television or newspaper, 

the world is really far away, and the nature 

Our instrument is still not 

working well enough and that is 

less good news. The tensions 

are starting to rise 

overwhelmingly close by. After a few days 

I find a routine, but not one I can get use to, 

as Antarctica is just too grand for that. 

shock because I think I’ve overslept. 

In the hangar the balloon gondola is being 

constructed on one side: telescope, star track - 

er, on-board computers, altitude control, 

communication et cetera. Under the telescope 

there is a free place for our cryostat, a gigantic 

thermos flask, which contains our cold 

optical instruments, detectors, and amplifiers. 

On the outside of the cryostat, the warm optics, 

signal generators (LOs), and electronics 

will be placed and a computer will control all 

of this as well. The integration is gradually 

more precise, the visit that my colleague 

Darren made. In the OB, you descend through 

more than two meters of ice into a small observation 

space surrounded by glass. When I 

tried to descend through the narrow tube into 

the observation space my claustrophobia got 

the better of me. You need to know your 

limits... Several days later they literally had to 

free somebody who could no longer move up 

or down. On YouTube you can find a film with 

the view underwater. Scott’s hut on Hut Point, 

constructed during his first expedition in 1902, 

still stands as if it were built yesterday. You

can only take a glimpse inside through the 

window: everything is still there as if he could 

return at any moment, including the halfbutchered 

animals. Really weird... 

The good news today is that we have just 

managed to get the entire signal chain of the 

4.7 THz receiver to work. A local signal enters, 

we see the sky and a desired signal emerges 

for the detector. Some optimization still needs 

to take place, but all of the stages work. 

The bad news is that the toilet is not working. 

cables are currently still exposed with a big 

risk of picking up undesirable signals. The 

biggest problem is ESD, ElectroStatic Dis - 

charge. Due to the desert environment and 

the low temperatures the air is extremely dry. 

Every movement that you make results in the 

build up of static electricity especially if you 

are wearing a fleece jumper. As soon as you 

touch something made of metal it sparks. 

These discharges are fatal for our instrument. 

Once everything has been incorporated there 

will be a reasonable degree of protection but 

that is not the case yet. We are all doing our 

reminds me of a story I read long ago about 

wildebeests if I remember correctly, (Google 

does not work). To determine which direction 

the herd should take, one of the animals occasionally 

stands up with its head in a certain 

direction, and then it goes and lies down 

again. If enough animals have looked in the 

same direction then the entire herd goes that 

way. 

Very indirectly, problems here are tackled in 

the same manner. Somebody says something, 

nobody appears to listen, somebody says 

25 


From now on it is the long drop: the Antarctic 

version of a privy, including snow swirling 

around and -10˚ C in the toilet. 

2 December 2015, Antarctica: 

best: we wear wrist straps to discharge static 

electricity, avoid artificial clothing, touch metal 

before we get near the instrument but a mistake 

can easily be made of course. 

something else. A solution is repeated by a 

third and a fourth, and suddenly we have 

chosen that direction. Fascinating. It works, 

but back in the Netherlands we do things very 

differently. 

the tension is mounting... 

The toilet has been repaired and that is a relief. 

The short drop is better in the long term. 

However our instrument is still not working 

well enough and that is less good news. The 

tensions are rising. Ideally you want to get 

this integration phase over and done with as 

quickly as possible. Many components and 

Seeing penguins is apparently 

a spiritual experience 

that changes you mentally 

In a nutshell, the instrument must be closed 

quickly and it must also function properly. But 

what is the right way forward? And when is it 

good enough? The decision-making process 

And then suddenly several large steps follow: 

the cryostat must be integrated with the telescope 

gondola. This interferes with our own 

work. The most vulnerable part, the local oscillator 

located on the outside, is taken off 

again. The calibration will therefore have to 

be repeated and the mounting plate that now

26 


already looks like a piece of Swiss cheese will 

probably have a few more holes added to it. 

However, a milestone has been achieved. 

We now have an almost completely working 

gondola in the hangar. 

10 December 2015, Antarctica: 

The Final Countdown? 

We are still steadily making progress. My 

current estimate is two to one: two days of 

progress and one day of setbacks. The date 

for the last big test, the hanging test, is 

20 December. According to the meteorologist 

apparently a spiritual experience that changes 

you mentally: people who have seen penguins 

will at convenient and not so convenient 

moments shove a phone under your nose 

with penguin photos and films. There is a 

sharp distinction, marked by jealousy and disbelief, 

between those who have seen and 

those who have not. I still belong to the latter 

group, as it appears that the penguins at 

Emmen Zoo do not count. Darren has seen 

them of course. 

the launch and I will even miss the hanging 

test. 

That is because no flights are made between 

17 December and 4 January, and then I would 

miss Christmas and New Year as well as 

several birthdays (including my daughter’s). 

STO-1 did not fly until 16 January. Very difficult. 

And I want to go home as I’ve been 

away since 17 October, but witnessing the 

launch is also a unique event of course. The 

final countdown: another four nights until 

the journey back. A 40-hour flight covering 

the desired airflow pattern at 40 km altitude 

has not developed yet. This is expected around 

18 December. So we are not losing any flight 

days yet. The balloon from our colleagues 

from GRIPS will probably be launched first and 

that will give us some extra breathing space. 

The sea ice is now starting to change. From 

vantage points in the neighborhood you can 

see the open sea coming closer on the horizon. 

The cracks in the ice are starting to move 

and penguins have been observed on the 

excursion to Cape Evans. Seeing penguins is 

During the past few weeks we have regularly 

said: it is Groundhog Day again (after the film 

with Bill Murray in the main role). Each day is 

more or less the same as the last, the same 

My current estimate is two 

to one: two days of progress 

and one day of setbacks 

daily routine, no change in routine due to 

weekend, clubs or other things that normally 

tell the days apart. But now the journey back 

home is approaching. So I will not experience 

31,000 km. What do I want, launch or 

family... 

4 Januari 2016, the Netherlands: 

Readjustment 

I’m back home again. The last days on Antarctica 

were really demanding: the lack of a 

daylight rhythm (and privacy) considerably 

disturbed my sleep. And I really cannot survive 

on four hours of sleep a night. That’s another 

thing I’ve learnt. The journey back was a long 

one. The modern C-17 from the journey 

inward had been replaced with a Hercules

uilt in a year before I was even born. It took 

this monster on skis eight hours to make the 

flight, and it sounded and felt as if somebody 

had attached a petrol-driven lawnmower to 

my back. But it flew and in the right direction. 

After landing in Christchurch I was really 

struck by the colors and smells after five 

weeks on Antarctica: it was an attack on my 

senses. Because snow and ice have no smells. 

And there is life, an awful lot of life: plants, 

insects, and birds of course but also people, 

especially strange faces: five weeks is clearly 

left Christchurch. On the Thursday morning of 

17 December I was back again in the Netherlands, 

exactly 2 months after I had left. Train, 

taxi, and at last home again. Embraced my 

So I will not experience 

the launch and I will even 

miss the hanging test 

wife and son, with our dog barking that he 

wanted to join in too. I also quickly picked up 

my daughter from school. Everything was 

back to normal again. 

team, which may launch first. Then it is our 

turn. 

The circulation pattern at 40 km altitude has 

now developed at the right location. On the 

ground the weather is less favorable, as the 

wind is a bit too strong to launch safely. 

GRIPS has already made three attempts. Time 

is now starting to run out: to be able to make 

a complete circle around the South Pole with 

a reasonable degree of certainty the flight 

must start by mid-January. However now 

things are in the hands of the weather gods. 

27 


enough to recognize and/or know a community 

of 1000 faces. 

I also acquired a completely new appreciation 

for comfort in the hotel room and a wellfunctioning 

Internet: click and it works, no 

more: click - coffee - check - more coffee - 

half a page. What a pleasure. 

The rest of the journey back seemed to take 

ages. Especially Tuesday, which I experienced 

twice due to crossing the International Date 

Line: I arrived earlier in Los Angeles than I had 

We are now two weeks further and it is the 

start of January. On Antarctica Darren Hayton 

and the rest of team have worked really hard. 

It is strange that I can now only follow them 

via email. The entire gondola works well and 

the last big hurdle, the hanging test, was 

successfully passed. During this test the 

gondola is hung outside and then it must be 

able to carry out all of the intended functions 

entirely autonomously. During the flight readiness 

review, the formal approval also came: 

we are allowed to fly! Now it is a case of 

waiting for good weather, first for the GRIPS 

And they are unpredictable: after a recordbreaking 

warm December my first workday 

after my Antarctic adventure starts with a 

white world in the Netherlands. 

That takes a bit of getting used to… 

WOUTER LAAUWEN 

(summarized and edited 

by Frans Stravers)

28 


THE MISSIONS TO DATE 

The instruments that SRON is currently making are intended for missions in five, ten or even more 

than fifteen years’ time. The scientific publications from now are from missions that are often still 

underway or have already been completed. An overview of the current missions and instruments.

Mission SRON contribution Studies mainly Description Status 

Herschel 

ESA 

2009 - 2013 

HIFI 

Heterodyne Instrument 

for the Far Infrared 

Universe 

> infrared 

The scientists used the far infrared light that HIFI 

captured in the search for molecules in the ’cold 

universe’. They demonstrated, for example, that 

ended 

the water on earth originated from comets. 

29 


XMM-Newton 

ESA 

1999 - ... 

RGS 

Reflection Grating 

Spectrometers 

Universe 

> X-rays 

The two ’M’s in XMM stand for multi-mirror. 

That refers to the hundreds of curved mirrors that 

capture the X-rays. SRON made the special spectrometers. 

operational 

Chandra 

NASA 

1999 - ... 

LETG 

Low-Energy Transmission 

Grating 

Universe 

> X-rays 

X-rays do not penetrate the earth’s atmosphere, 

so a satellite is needed to measure these. Chandra, 

for example, has a spectrometer for ‘soft X-rays’. 

SRON made the ring-shaped core of the spectrometer. 

operational 

INTEGRAL 

ESA, NASA 

and RKA 

2002 - ... 

Advice during 

construction, calibration, 

and research 

Universe 

> visible, 

X-rays, 

and gamma 

The name INTEGRAL is not just the acronym for 

INTErnational Gamma-Ray Astrophysics Laboratory. 

It also stands for the integral package of radiation 

that the satellite observes. Besides gamma 

radiation the satellite can also observe X-rays and 

visible light. 

operational 

ALMA (Chili) 

ESO 

2011 - ... 

High-frequency 

receivers 

Universe 

> (sub)millimeter 

ALMA in Chile is the largest astronomical project 

in the world. 66 radio antennae of 7 to 12 meters 

in diameter receive signals from the universe. 

SRON was the technical consultant during the 

development and construction of the highfrequency 

receivers and is assisting in their use. 

operational 

MetOp 

ESA and 

EUMETSAT 

2006, 2012, 

2017 

Calibration, data 

processing GOME-2 

Global Ozone 

Monitoring Experiment 

Earth 

> visible light 

The MetOp project is successively bringing three 

satellites into orbit around the poles. The satellites 

carry out measurements on the weather and the 

climate. SRON collaborated on the development 

of the ozone meter and is helping to analyze the 

results. 

under 

development/ 

operational

30 


Mission SRON contribution Studies mainly Description Status 

APEX (Chili) 

ESO 

2014 

A-MKID-camera 

Apex Microwave 

Kinetic Induction 

Universe 

> between 

infrared and 

The core of the A-MKID consists of 20,000 pixels, i.e. 

detectors. The astronomers can read all of the pixels 

indi vi dually. From the ground they can see three times 

under 

development 

Detector 

radio 

more sharply than the detectors onboard the space 

telescope Herschel. 

ASTRO-H/ 

Hitomi 

JAXA, NASA 

and ESA 

2015 

SXS 

Soft X-ray 

Spectrometer 

Universe 

> X-rays 

Sometimes X-rays are so strong that they overpower 

the sensitive spectrometers. SRON made the filter wheel 

that prevents overpowering due to strong radiation. 

The institute also developed the calibration source: an 

X-ray emitter on board with precisely known properties. 

operational 

Sentinel-5 - 

precursor 

ESA and EU 

2016 

Immersed gratings, 

read out electronics 

TROPOMI, derivation 

specifications, calibration, 

data retrieval, 

TROPospheric Ozone 

Monitoring Instrument 

Earth 

> ultraviolet, 

visible, 

infrared 

Sentinel-5-precursor is the successor to the environmental 

satellite ENVISAT. The Tropomi instrument combines the 

large wavelength range of its predecessor SCIAMACHY 

with the wide observation angle of the OMI instrument. 

SRON/TNO made the ingenious ‘immersed grating’. 

ready for 

launch 

STO2 

NASA 

2016/2017 

Three THz receivers 

(4.7, 1.9 and 1.4 Thz) 

and the 4.7 terahertz 

local oscillator unit 

Universe 

> far infrared 

The balloon mission STO2 will map part of the cosmos 

during its flight 40 km above Antarctica. STO2 will observe 

the emission lines of carbon (CII) and nitrogen (NII) 

at a frequency of 1.9 and 1.4 terahertz respectively. 

With the new 4.7 terahertz technology STO2 will also 

observe the emission lines of electrically neutral oxygen. 

ready for 

launch 

SPICA 

JAXA and 

ESA 2028 

SAFARI 

SpicA FAR-infrared 

Instrument 

Universe 

> far infrared 

SAFARI is the successor to the molecule hunter HIFI. 

The spectrometer/camera will look deeper and in greater 

detail than ever before into the universe from an infrared 

perspective. 

under 

development 

ATHENA 

ESA 

2028 

Detectors and readout 

electronics X-ray 

Integral Field Unit 

Universe 

> X-rays 

ATHENA is the selected successor to ASTRO-H/Hitomi, 

which was launched in February 2016. SRON is working 

together with groups from Japan and the United States, 

for example, to make a state-of-the-art, supercooled 

spectrometer. 

under 

development

31 


Mission facts 

> Uncertainty: If the mission is planned far 

into the future then it is still often uncertain 

whether the mission will go ahead, when 

the launch will take place exactly, and which 

instruments will be allowed on board. 

Missions that are currently flying often have 

a far longer mission duration than planned. 

The mission duration is often estimated 

conservatively to prevent disappointments. 

Chandra was planned to do service from 

1999 until 2004 but it is still working in 

2016. 

> Specialism: astronomers distinguish 

seve ral types of light and radiation: radio, 

infrared, visible light, ultraviolet, X-rays, 

gamma. Each telescope has its own special - 

ism and views the universe through differ ent 

eyes. 

> International: JAXA is Japanese, RKA is 

Russian, ESA is European, NASA is American, 

ESO is the European Southern Observatory 

in Chile, and EUMETSAT is the European 

organization for meteorological satellites.

32 


CREDITS 

SRON Spectrum is the newsletter of SRON Netherlands Institute 

for Space Research 

SRON’s mission is to bring about breakthroughs in international 

space research. Therefore the institute develops pioneering 

technology and advanced space instruments, and uses them to 

pursue fundamental astrophysical research, earth science and 

exoplanetary research. 

As national expertise institute SRON gives counsel to the Dutch 

government and coordinates national scientific contributions to 

international space missions. SRON stimulates the implementation 

of space science in our society. SRON is part of the Netherlands 

Organisation for Scientific Research (NWO). 

To register for SRON Spectrum or to cancel your subscription 

please send an e-mail to info@sron.nl. 

Text Frans Stravers, Eveline van der Linden, 

Yannick Fritschy, Marieke Baan and 

Wouter Laauwen 

Photos SRON, NASA, ESA, JAXA 

Design Studio WW15 

Printed by Drukkerij Badoux, Houten 

Published by SRON Netherlands Institute for Space Research 

Address Sorbonnelaan 2 

3584 CA Utrecht 

+31 88 777 5600 

Landleven 12 

PO Box 800 

9700 AV Groningen 

+31 50 363 4074 

Mail info@sron.nl 

Web sron.nl 

Facebook facebook.com/sron.nl 

Twitter @SRON_Space 

Youtube youtube.com/SRONruimteonderzoek

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