Mission Information

RHESSI was funded by NASA's Explorers Program (http://explorers.gsfc.nasa.gov/) under the category of "Small Explorers." These are relatively low cost missions, which have specific scientific objectives that are in line with a list of NASA space science priorities.

RHESSI Science
Principal Investigator Robert Lin explains sun science and RHESSI mission objectives. Featuring satellite data and images of the Sun.
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Why did this mission happen, and why was it considered important enough for NASA to fund it?
RHESSI helped us answer one of the most fundamental questions about how the sun works: How do solar flares release such large quantities of energy in such a short span of time? (A single flare can be as powerful as ten million volcanic explosions!). For an excellent scientific overview and a complete rationale for the mission, read the RHESSI Online Brochure
Why did RHESSI make observations of the Sun from space? Couldn't the same data have been collected from Earth?
A very large part of the expense of the RHESSI mission was allocated to its launch into space. This was necessary because x-rays and gamma rays do not penetrate the Earth's atmosphere. Thus, RHESSI's observations were made from space. In fact, before the advent of space-based observatories, there were only limited astronomical observations done in the high energy portion of the electromagnetic spectrum. To understand why, see Atmospheric Transmission, or study this diagram (scroll down to the bottom of the page).
What was special about the RHESSI mission?
The centerpiece of the RHESSI mission was the imager, which used a new technology to capture images and spectra of high energy solar flares. The imager used a method which is quite unlike the cameras and telescopes that are familiar to us; it had no lenses! Learn more about the RHESSI Imager.

Participating Institutions and their responsibilities.

University of California at Berkeley, Space Sciences Laboratory (SSL at UCB) - (http://hessi.ssl.berkeley.edu/)
NASA Goddard Space Flight Center (GSFC), Greenbelt, Maryland - (http://hesperia.gsfc.nasa.gov/hessi/)
Paul Scherrer Institute Switzerland - (http://hessi.web.psi.ch/)
Spectrum Astro Aerospace Company, Gilbert Arizona - (http://www.spectrumastro.com/ProgramsProducts/Hessi.asp)

Basic information about RHESSI from the Goddard Space Flight Center and UC Berkeley RHESSI Web sites:

Fact Sheet (including scientific objectives) http://hesperia.gsfc.nasa.gov/hessi/sheet.htm

Online Brochure (complete scientific background and rationale for the mission) http://hesperia.gsfc.nasa.gov/hessi/brochure.htm

Mission Concept (slightly technical description of the mission) http://hesperia.gsfc.nasa.gov/hessi/concept.htm
RHESSI Spacecraft: http://hessi.ssl.berkeley.edu/spacecraft/
RHESSI Launch
Mission Control at the Mission and Science Operations Center (MSOC) at SSL http://hessi.ssl.berkeley.edu/ground_systems/

Links to Related Sites

Current Solar Science Space Missions

Yohkoh http://www.lmsal.com/SXT/homepage.html
A joint mission between Japan and the U.S. which has been studying the sun in x-rays and gamma rays since 1991.
Yohkoh Mission Public Outreach (YPOP) http://www.lmsal.com/YPOP/
SOHO http://sohowww.nascom.nasa.gov/
A joint mission between the European Space Agency (ESA) and NASA which has been studying the sun since 1995. SOHO's excellent ultraviolet images and movies of solar activity are frequently seen in the media.
SOHO Explore http://sohowww.nascom.nasa.gov/explore/
TRACE http://vestige.lmsal.com/TRACE/
A NASA mission launched in 1998 (with the same Pegasus launch vehicle that will launch RHESSI) which is studying the fine details of the sun's magnetic activity.
TRACE Outreach Page http://vestige.lmsal.com/TRACE/Public/eduprodu.htm
ACE - (http://www.srl.caltech.edu/ACE/)
A NASA mission launched in 1997 to study the chemical composition of the solar wind.

Cosmic and Heliospheric Learning Center (from ACE) http://helios.gsfc.nasa.gov/
IMAGE http://image.gsfc.nasa.gov/
A NASA mission that will be launched in early 2000 to study the global response of the Earth's magnetosphere to
changes in the solar wind.
IMAGE Public Outreach and Education http://image.gsfc.nasa.gov/poetry/
Project Starshine http://www.azinet.com/starshine/
A unique mission which is heavily based upon student participation. The starshine satellite was launched from the Space Shuttle in the spring of 1999 to study the effect of solar activity upon the density of the Earth's upper atmosphere.
Ulysses http://ulysses.jpl.nasa.gov/
A joint mission between the European Space Agency (ESA) and NASA which was launched in 1990. Ulysses is in a unique orbit which carries it high above and below the sun's north and south poles to get a view of the sun we could never have from earth.
Genesis http://www.genesismission.org/
A NASA mission that will collect samples of the solar wind and return them to Earth for study. To be launched in 2001

International Solar-Terrestrial Physics http://www-istp.gsfc.nasa.gov/
"A global concert of spacecraft and observatories, scientists and engineers, tuning into the Sun, the Earth, and their never-ending symphony..."
Polar http://www-spof.gsfc.nasa.gov/istp/polar/
Launched in 1996, it images the Earth's auroras and is very useful for viewing the effects of the solar wind and geomagnetic storms. It's photographs of auroras are quite spectacular.
Links to even more solar space missions: - (http://sunearth.gsfc.nasa.gov/edmissns.htm)
From the Sun-Earth Connection Forum

Other High Energy Space Missions

Chandra X-ray observatory - (http://chandra.harvard.edu/index.html)
One of NASA's series of "Great Observatories" in space.
FUSE http://fuse.pha.jhu.edu/index.shtml
EUVE - (http://ssl.berkeley.edu/euve/)
Extreme Ultraviolet Explorer
Compton Gamma Ray Observatory http://cossc.gsfc.nasa.gov/cossc/
Launched in 1991.

Important NASA Web Pages

NASA Office of Space Science http://spacescience.nasa.gov/