LEO
Heliophysics
RHESSI
Space-based Solar Flare Observatory
FACTS AT A GLANCE
Mission Description
The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) is a NASA Small Explorer
(SMEX) space observatory with a primary mission to explore the basic physics of particle acceleration
and explosive energy release in solar ares. RHESSI combines, for the rst time, high-resolution imaging
in hard X-rays and gamma rays with high-resolution spectroscopy, allowing a detailed energy spectrum
to be obtained at each point of the image.
Orbital was responsible for the initial concept study, followed by the design and manufacture of the
spacecraft. Orbital also participated in the integration and test of the payload at the University of
California at Berkeley.
®
RHESSI was launched in February 2002 on an Orbital Pegasus
Air Force Station to begin a two-year mission. At the end of the two years, RHESSI’s net spacecraft
availability was 100 percent and the mission was extended. After more than ten years, RHESSI
continues to collect and download data.
XL rocket from Cape Canaveral
Spacecraft
The spacecraft, derived from Orbital's LEOStar™-2 core design, provides a mature, reliable platform
with a VME-based modular architecture and a RAD6000 Central Processing Unit (CPU). The attitude
control functions include a spin control mode for adjustment of the vehicle spin rate to a commandable
value, and a normal mode to keep the spin axis pointed at the sun.
Placing the equipment deck, solar array wings, and the majority of the electronic components near the
spacecraft center of mass provides a symmetrically balanced, stable platform for the spin-stabilized
attitude control system.
• Launched February 5, 2002 on
an Orbital Pegasus XL from Cape
Canaveral Air Force Station, Florida
• 600 km circular, 38° inclination, Low
Earth Orbit mission
• RHESSI successfully completed its
two-year mission in March 2004 and
continues to collect on-orbit data
• The onboard instrument observes
and collects X-ray and gamma ray
emissions with an unprecedented
combination of high-resolution imaging
and spectroscopy
Customer:
University of California at Berkeley
RHESSI in Orbital's Gilbert, Arizona satellite
manufacturing facility
RHESSI
Specications
Spacecraft
Launch Mass: 291 kg (641.5 lb.)
Solar Arrays: Four deployable wings, triple-junction GaAs
cells, 505 W EOL
Orbit: 600 km circular @ 38
°
inclination
Stabilization: Spin @ 15 RPM
Pointing Knowledge: 324 arcsec (3s)
Data Storage: 32 Gbits
Data Downlink: 4 Mbps, S-band (CCSDS, STDN)
Propulsion: None
Mission Life: 2 years
Current Status: Operational
Launch
Launch Vehicle: Pegasus
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XL
Launch Site: Cape Canaveral Air Force Station, Florida
Date: February 5, 2002
Instrument
Imager/Spectrometer
The imager is a 1.7 meter long carbon ber composite tube with grid tray
assemblies at each end. The grid trays are aluminum structures with nine sets
of collimating grids in each tray. The spectrometer is a cryostat containing the
nine germanium detectors. The nine sets of grids in the imager are required to be
aligned with the nine detectors in the spectrometer. Rotation of the spacecraft
causes the ux of high energy particles in the eld of view of the instrument to
be modulated by the collimating grids. The instrument covers energies from soft
X-rays (3 keV) to high-energy gamma-rays (20 MeV).
Mission Partners
University of California at Berkeley
Procuring agency. Program management and science
lead. System integrator, and operator of satellite on-orbit.
Developer of the instrument spectrometer.
Orbital Sciences Corporation
Contractor for spacecraft design and manufacture, with
support to payload integration and system test
NASA Goddard Spaceight Center
Mission management, technical oversight, and data
archiving. Developer of the instrument grids and
cryocooler.
Paul Scherrer Institut (Switzerland)
Developer of the imaging telescope and optical aspect
system for the payload instrument
Data Availability
Unlike most other scientic missions, there are no proprietary data rights.
All data, and the software needed to analyze them, are freely available online.
This allows many talented scientists around the world to analyze RHESSI data
along with the complementary observations of the same ares that are available
from other instruments in space and from ground-based observatories. For more
information, visit: http://hesperia.gsfc.nasa.gov/rhessidatacenter.
Orbital Sciences Corporation
45101 Warp Drive
©2014 Orbital Sciences Corporation FS004_11_2998
•
Dulles, Virginia 20166
•
www.orbital.com
A solar are reconstructed by the RHESSI "Image Widget."
(Graphic courtesy NASA)
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