The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity

HEO
(1) Highly elliptical orbit. Definitions vary, one being an
orbit with a perigee (low point) below 3,000 km and an
apogee (high point) above 30,000 km. (2) High Earth
orbit. An orbit whose apogee lies above that of a geostationary
orbit at 35,800 km.
HEOS (Highly Eccentric Orbiting Satellite)
ESRO (European Space Research Organisation) satellites
that traveled in extremely elongated orbits in order to
study the interplanetary magnetic field outside Earth’s
magnetosphere. (See table, “HEOS Missions.”)
Hermes
A proposed small, manned space plane for servicing
European components of the International Space Station.
It began as a purely French project, but as development
costs increased, France managed to obtain other
European funding, primarily from Germany, for development
of the craft. Hermes would have provided independent
European manned access to space, and the
weight growth of the spacecraft during design and development
was a major influence in the specification for the
Ariane 5 launcher. Hermes was intended to take three
astronauts to orbits of up to 800-km altitude on missions
lasting 30 to 90 days. Payload to be returned to Earth
could be contained in a small payload bay, but most
experiments were to be carried in an expendable pressurized
supply module equipped with a docking port and
mounted to the base of the glider. After the Challenger
disaster, many safety features were added to Hermes,
leading to further increases in weight and cost. In an
emergency the crew cab could have been separated from
the remainder of the glider. Later, however, the crew
escape capsule idea was abandoned and was replaced by
three ejection seats to save weight. Hermes was to have
been launched atop an Ariane 5 by 1998, but by 1992,
estimated development costs rose to DM 12 billion and
the project was abandoned.
Hero of Alexandria (A.D. 1st century)
Greek inventor of the rocketlike device called an aeolipile.
He lived about three centuries after another ancient
rocketeer, Archytas.
HEOS Missions
HETE (High Energy Transient Experiment) 183
Herschel Space Observatory
A giant ESA (European Space Agency) space telescope
with a 3.5-m-diameter main mirror (by comparison, Hubble’s
is only 2.4 m across) designed to observe the universe
in unprecedented detail at far infrared and
submillimeter wavelengths from 80 to 670 microns and
to carry out sensitive photometry and spectroscopy. Herschel
will be launched together with Planck in early 2007
by an Ariane 5. Once in space, the two satellites will separate
and proceed to different orbits around the L2
Lagrangian point, some 1.5 million km from Earth. Herschel,
named after the great Hanoverian-born British
astronomer William Herschel (1738–1822), was previously
known as FIRST (Far Infrared and Submillimetre
Space Telescope).
HESSI (High Energy Solar Spectroscopic Imager)
See RHESSI.
HETE (High Energy Transient Experiment)
A satellite whose main task is a multiwavelength study of
gamma-ray bursts using ultraviolet, X-ray, and gamma-ray
instruments. A unique feature of the mission is its ability
to localize bursts with an accuracy of several arcseconds
in near real-time. These positions are transmitted to the
ground and picked up by a global network of primary
and secondary ground stations, enabling rapid follow-up
studies. The original HETE was lost following its launch
on November 4, 1996, when it (and its co-passenger,
SAC-B) failed to separate from the third stage of a Pegasus
launch vehicle. However, the scientific importance
and continuing relevance of the mission provided the
impetus for the mission collaborators, including NASA,
CESR (Centre d’Etude Spatiale des Rayonnements),
CNES (the French space agency), and RIKEN (Japan’s
Institute of Chemical and Physical Research), to fund a
replacement satellite. HETE-2 retains nearly all the original
HETE design elements but carries a soft (longer wavelength)
X-ray camera in place of the original ultraviolet
cameras. Its main instrument is FREGATE, the French
Gamma Telescope, a hard (shorter wavelength) X-ray
spectrometer operating in the 6 to 400 keV energy range.
This gamma-ray burst detector, together with a Wide
Field X-ray Monitor, is used to trigger searches with the
Spacecraft Date
Launch
Vehicle Site Orbit Mass (kg)
HEOS 1 Dec. 5, 1968 Delta E Cape Canaveral 20,020 × 202,780 km × 60.5° 108
HEOS 2 Jan. 31, 1972 Delta L Vandenberg 405 × 240,164 km × 89.9° 123