TopSat-Assessing the Military Utility of a Tactical ISTAR Demonstrator

6th Responsive Space Conference
RS6-2008-6003
TopSat-Assessing the Military
Utility of a Tactical ISTAR
Demonstrator
H.S. Jolly
Defence Science Technology Laboratory, UK
T. Burt
Royal Air Force, UK
D.W. Beard
Defence Science Technology Laboratory, UK
6th Responsive Space Conference
April 28–May 1, 2008
Los Angeles, CA

AIAA-RS6-2008-6003
TopSat- Assessing the Military Utility of a Tactical ISTAR
Demonstrator
H. S. Jolly
Defence Science and Technology Laboratory
Dstl Information Management Department, Portsdown Hill, Fareham, PO14 6AD, UK
HSJolly@dstl.gov.uk
T. Burt
Royal Air Force, MoD Main Building, London, SW1A 2HB, UK
D.W. Beard
Defence Science and Technology Laboratory
Dstl Joint Systems Department, Portsdown Hill, Fareham, PO14 6AD, UK
DWBeard@dstl.gov.uk
ABSTRACT
Launched on 25 October 2005, TopSat is a small (

AIAA-RS6-2008-6003
INTRODUCTION
TopSat is a small, (~108kg) low-cost (

AIAA-RS6-2008-6003
Off nadir
viewing
capability
axis aspheric design
Body pointing capability
of ± 30º in two axes
The TUG was chaired by MoD EC(ISTAR) and its
roles were to define the user community requirements
and to prioritise TopSat tasking. The TUG met bimonthly
and was the primary vehicle for the
coordination of the assessment of the system’s utility.
THE GENERAL ASSESSMENT OF MILITARY
UTILITY
Downlink
X-band and
S-band
Ground
stations
10M bits/second
Fixed ground station at
West Freugh in Scotland
with a 13m dia. dish and
links at S and X-band.
Transportable ground
station (RAPIDS) with a
3m dia. dish and X-band
link
Lifetime 1 year Exceeded
To ground stations in
line of sight
TopSat can be employed in two distinct roles:
a. In a standard role with tasking and data down-linked
via the QinetiQ ground-station at West Freugh.
b. In a tactical or in-theatre operational role with
tasking by deployed units, and the use of the mobile
ground-station RAPIDS for local data down-linking.
For MoD operations, data was always down-linked to
West Freugh, even when RAPIDS was used in theatre.
MoD USERS AND THE USE OF IMAGERY
Prior to the launch of the satellite, the TopSat
Consortium contacted representative from a range of
potential user organisations within MoD. These were
either existing exploiters of imagery or headquarters
units. In many cases they were unfamiliar with
intelligence, surveillance, targeting and reconnaissance
(ISTAR) satellites that could be tasked directly. This
group, the TopSat Users Group (TUG), was expanded
to include representatives from the US Air Force
Research Laboratory (AFRL) and Defence Research
and Development Canada (DRDC) who were
collaborating with Dstl under the Trinational
Technology Research and Development Programme.
Military utility assessments can be carried out in two
complementary, ways:
a. By using operational analysis (OA) methods
such as modelling to evaluate the contribution of the
systems in representative scenarios. This approach
cannot include all the real world features and is only as
good as the assumptions that are used (including the
user requirements) but does provide a broad answer
over a range of conditions.
b. Operational experimentation trials. This
approach can provide practical experience and valuable
insights into the operation of systems. It can also
provide opportunities to explore concepts of use and for
interactions between users and system specialists.
However, it is necessarily limited in terms of the range
of applications and conditions that can be explored.
The work presented within this paper concentrated on
the second approach only.
ASSESSMENT
Because of the importance of the Intelligence Cycle;
Direct, Collect, Process and Dissemination (DCPD), the
military utility assessment of TopSat was evaluated
against each element separately.
The assessment was carried out for the complete
TopSat system comprising; the satellite, ground stations
and operations infrastructure.
Direct
The Direct activity includes the tasking of the satellite,
scheduling of collection and prioritising the tasks. It
concludes on the receipt of the confirmation of
acceptance by the satellite operator to the User.
User tasking of TopSat was, via a direct interface
(telephone or/and e-mail) to the TopSat Payload
Operations Centre, operated by QinetiQ, in
Farnborough UK.
Imagery requestors were defined as either ‘remote’ or
‘local’:
a. A remote requestor having a requirement for TopSat
imagery would place a request direct with the TopSat
Consortium’s point of contact, with the necessary
image acquisition procedures, and also provide
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instructions for the dissemination of the acquired data
to the requestor.
b. A local requestor was one deployed in situ with the
RAPIDS mobile ground station. Here the requestor
would place their image request directly with the
TopSat Consortium staff deployed with RAPIDS. The
request was then relayed and agreed with the TopSat
Payload Operations Centre in Farnborough using voice
or data communication routes.
The TopSat Industrial Consortium did not set tasking
priorities, requiring instead, MoD to set them. Because
the image capacity of the system was low, conflicts in
tasking priorities did not arise. However, for any future
operational system, users agreed that some mechanism
to set task priorities would be required if conflicts in
tasking requests are to be avoided.
In an attempt to manage request co-ordination between
the multiple TopSat users, the internet based TopSat
Image Request Analysis Tool (TIRAT) was produced
by the TopSat Consortium to display the location of
TopSat image requests and collected images. This was
intended to allow users to identify where their requests
overlapped with those of other image requestors or to
identify images already taken which satisfied the image
requirement. The initiative illustrated the requirement
for an easy to use imagery request tool, both for users
and for the managers of such systems.
TopSat tasking also demonstrated the need to
incorporate meteorological data into the scheduling and
tasking process as cloud cover over targets reduced the
number of usable images to approximately 60% of the
total taken during all MoD trials.
The time taken to Direct the sensor was driven by the
time taken for the satellite to be in line of sight of the
tracking, telemetry and command (TT&C) ground
station for upload of the tasking. The maximum time
for this process was twelve hours. This period could,
for a future operational system, be reduced by the use
of multiple ground stations or/and through the use of
command relay satellites to the time taken to request
that image, schedule the sensor in order of the priority
of the request and respond to the requester with an
expected time of delivery of the image; a total period of
the order of a few hours, depending on the scheduling
and request co-ordination tasks (and the number of
satellites in the constellation).
No specific experiments were conducted to probe the
Direct aspect of the TopSat System’s utility.
Consequently, the assessments were based on
examination and feedback from the users post trials.
Collect
Collection for a satellite system can be considered as
the process of the transit to the target location after
receipt of the command, collecting the image of the
target location and then downloading the image data to
a ground station.
The time taken for a single space-based sensor to access
a geographic location of interest is largely set by the
orbital motion and the field of regard of the satellite.
Consequently the duration of the collection process can
be, for single satellite system such as TopSat, up to
about three days depending on the location of the target.
This interval could be reduced to at least once a day if a
constellation of 3 or more satellites or tuned orbits were
used. As a result, this aspect of the utility of the TopSat
system must be viewed in the context of assessing a
demonstrator system as opposed to an operational
constellation consisting of several satellites.
Reliance on the TDI function to mitigate the low signal
to noise ratio of the small aperture imager means that
the TopSat imager is able to capture no more than 1-2
images per pass. Furthermore, the TDI driven
requirements for satellite agility also means that the
satellite is also power limited due to the use of body
mounted solar panels (as opposed to larger, deployable
ones). Consequently the capabilities of TopSat have
been limited by its small size.
Although close to the demonstrator satellite’s
specification, the probability of imaging a target within
an image of ~70% was considered too low for an
operational system due to the use of earth-horizon
sensors over star trackers.
Process
The Process task can be defined as the activities
required to turn the raw data received by the satellite
ground-station to usable intelligence, in whatever form.
The time taken to process the data into JPEG or TiFF
files was measured in hours. To process these into georeferenced/rectified
image products (GeoTIFF) image
reference points archived from other systems, such as
LandSat were used. Consequently, from a strategic
aspect, the data was of use but from a tactical or
operational use, the data would have had limited value,
particularly for maritime surveillance where no land
features were imaged. This and the uncertainty of the
© British Crown copyright-Dstl 2008 – published with the permission of the Controller of Her Majesty’s Stationary Office
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geographical location of the centre point of any image
due to the pointing errors of the TopSat system were
considered to limit the utility of the TopSat products.
Some tactical/operational users indicated that JPEG
files of TopSat imagery provided as much information
as TiFF files near a tenth of the file size. As tactical
users require image data in small files that can be sent
and received quickly over limited bandwidth links (i.e.
to facilitate timely dissemination); they do not,
typically, require large detailed images, particularly if
the equipment to support the products is unavailable or
of limited supply in theatre. As a consequence of these
issues, GeoTIFF or, preferably, geo-rectified JPEG
processed to allow mensuration were considered to be
the optimum file format for the tactical user with higher
levels of processing being carried out for strategic
purposes in slower time.
Disseminate
Dissemination is the distribution of information or
intelligence to the appropriate decision maker.
Typically, the dissemination function consisted of the
production of a CD-ROM by the TopSat consortium for
dispatch by Royal Mail or courier to the User. This
dissemination process was used as the TiFF data files
were too large to send be e-mail.
The aspect of the dissemination process that impacted
on the utility of the system the most was transferring
the large data files to the tactical users. Consequently,
experiments were undertaken to explore the key issue
of data dissemination. These included:
• The use of commercial (Inmarsat Ltd) satellite
broadband global area network services (BGAN) to
transfer JPEG TopSat images directly to a User in
theatre;
• The use of RAPIDS located near to the telemetry,
tracking and telecommand ground station to
demonstrate the tasking, image collection and
download in a single satellite pass.
The latter test demonstrated that very high timeliness
and freshness of imagery is feasible; a responsiveness
(image request to delivery) of

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Figure 1 – TopSat Image Clip of Cairo, Egypt, showing pyramids, March 2007
• Users preferred higher resolutions than 1m,
but not at the expense of field-of-view; the
minimum size being considered as acceptable
for most applications being approx 10km by
10km. Figures 1 is an example image clip
from TopSat, courtesy of QinetiQ Ltd showing
the pyramids near Cairo, Egypt.
• Georeferenced and georectified data was
considered to be critical to all users to allow
mensuration and geolocation from the images.
• For all applications considered, accurate
ephemeris and sensor pointing data is required.
The pointing accuracy specification of TopSat,
providing an approximately 70% probability
of collecting an image of a point target within
its field of view, is too low for an operational
system.
• For the majority of tactical and operational
applications, compressed JPEG imagery was
acceptable.
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• 100% overlap between the multi-spectral and
PAN imagery would have been preferable to
the large off-set provided by TopSat. This
would have allowed the production of PAN
sharpened multispectral images, combining the
benefits of the higher resolution PAN images
with the additional information from the
multispectral images.
• Rapid revisit (