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.
Principal Investigator Robert Lin explains sun science and RHESSI mission
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
- 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
Participating Institutions and their
Basic information about RHESSI from the Goddard Space Flight Center and UC
Berkeley RHESSI Web sites:
Sheet (including scientific objectives) http://hesperia.gsfc.nasa.gov/hessi/sheet.htm
Online Brochure (complete scientific background and rationale for the
Mission Concept (slightly technical description of the mission) http://hesperia.gsfc.nasa.gov/hessi/concept.htm
- 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
- 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.
Outreach Page http://vestige.lmsal.com/TRACE/Public/eduprodu.htm
- ACE -
A NASA mission launched in 1997 to study the chemical composition of the
- 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
- 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
- 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
Other High Energy Space Missions
- International Solar-Terrestrial
"A global concert of spacecraft and observatories, scientists and
engineers, tuning into the Sun, the Earth, and their never-ending
- 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
Important NASA Web Pages
- 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.
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