The Combined Release and Radiation Effects Satellite (CRRES), a joint NASA/Air Force project, will attempt to learn more about the hostile environment often referred to as "the vacuum of outer space."
Outer space, however, is not empty. It is a dynamic mix of invisible magnetic and electric fields, energetic particle radiation and electrically charged plasmas, collections of negatively charged electrons and positively charged atoms whose interactions are influenced by long-range electric forces, rather than by the atomic collisions that govern the behavior of neutral gases.
Complex interactions involving these fields and particles extract energy from the solar wind, a continual flow of particles from the Sun, and deposit much of this energy into the Earth's upper atmosphere, ionosphere and magnetosphere. The Earth's neutral atmosphere, extending approximately 40 miles above the Earth's surface, is a shell of neutral gases that encompasses the Earth's weather and protects its life. The ionosphere, which extends from above the atmosphere to approximately 620 miles above the Earth, is an electrically charged transition zone between the atmosphere and the magnetosphere.
Beyond the ionosphere lies the magnetosphere, populated with energetic, charged particles. When this magnetosphere is hit by a cloud of energetic particles from a solar flare, a so-called geomagnetic storm can occur that can disrupt power systems and long-distance communications. Today's increasingly complex satellites, carrying sophisticated electronics and sensors such as the Tracking and Data Relay Satellite and other geostationary spacecraft, are susceptible to damage from solar energetic particles that can limit the satellite operational lifespan.
Scientists have been studying the magnetosphere for decades, using a combination of ground-based measurements and satellite observations. Beginning this summer, the CRRES satellite will conduct experiments allowing direct observations of the Earth's magnetic field.
[back to contents]CRRES will carry 24 canisters containing various chemicals. For each experiment, one or two canisters will be ejected by the spacecraft. Approximately 25 minutes later, after the canister and spacecraft are far enough apart to prevent contamination, the canister will release its chemical vapors. The chemical will be ionized by the Sun's ultraviolet light, creating luminous clouds initially about 60 miles in diameter. The clouds will elongate along Earth's magnetic field lines, briefly "painting" these invisible structures so that they become visible.
By observing the motion of the clouds, scientists will be able measure electric fields in outer space, to "see" how these fields interact with charged particles to form waves and to better understand how the Earth extracts energy from the solar wind. These clouds will be studied by instruments on the ground, in specially equipped aircraft and aboard CRRES itself. The CRRES releases will be augmented by releases from sounding rockets to conduct further experiments.
The CRRES program is the latest in a new generation of space research missions studying earthspace, the space environment just above Earth's atmosphere, through complementary, active experiments and passive observations. CRRES is a joint program of NASA, through its Marshall Space Flight Center, and the Department of Defense's (DOD) Air Force Space Test and Transportation Program. NASA's role in the mission is the release of tracers. The DOD experiments will measure the natural radiation in space and its effects on microelectronics.
The satellite was built by the Ball Aerospace Systems Group, Boulder, Colo. The scientific instruments and investigations are being supplied by scientists from institutions throughout the United Sates, Europe and South America.
[back to contents]In 1984, the CRRES satellite was designed as a dual-mission spacecraft carrying 48 canisters of chemicals for release. The spacecraft initially was to be deployed from the Space Shuttle in a low-Earth-orbit (LEO) of 215 miles altitude. At LEO it would have performed chemical release experiments for 90 days. Following the LEO mission, a trans-stage motor would have placed CRRES in a geosynchronous transfer orbit (GTO), where additional chemical releases and the primary DOD mission would be carried out.
The loss of Challenger in January 1986 forced a major restructuring of the CRRES Program. In June 1987, NASA decided to launch CRRES directly to GTO on an Atlas-Centaur carrying 24 canisters, complemented by a program of sounding rocket launches to perform some of the experiments deleted from the original 48-cannister CRRES mission.
[back to contents]The 24 canisters on the CRRES/GTO mission will perform 14 experiments. Seven of these will be undertaken at altitudes ranging from 1,200 to 21,000 miles (the original GTO releases). The remainder will be undertaken near perigee at altitudes between 240 and 300 miles.
The mission will be complemented by 10 sounding rockets to perform releases that require precise targeting of location, local time and altitude. Six rockets are to be launched from Puerto Rico and four from Kwajalein, Marshall Islands.
[back to contents]The successful execution of the chemical release experiment demands a wide variety of diagnostics. Principal ground-based facilities that will monitor and track the releases include the Arecibo Incoherent Scatter Radar and the Arecibo HF Ionospheric Heater Facility in Puerto Rico, the Jicamarca (Peru) Radar Facility, the ALTAIR Radar Facility at Kwajalein and the Millstone Hill Radar Facility in Massachusetts.
These facilities will be used to diagnose the state of the ionosphere prior to, during and just after each release. They also will examine in detail the structure of the artificial plasma clouds. The radars can measure the state of the ionosphere and artificial plasma clouds simultaneously over a wide altitude range.
The DOD scientific instruments will complement the CRRES chemical-science mission, measuring the effects of the releases at close range. For releases, the instruments will measure the state of particles and waves in the magnetosphere and assess whether a large magnetic storm is imminent. This will help the scientists determine the best time to conduct a release.
No less important will be an array of ground- and aircraft-based optical diagnostics, including wide-field cameras, high-sensitivity television systems, spectrographs and interferometers. Portable VHF coherent scatter radars will diagnose regions not accessible to the fixed radars, and radio receivers on board aircraft will measure disruptions in signals received from satellites resulting from the ionospheric disturbances.
(See DETAILED EXPERIMENTS DESCRIPTION section of this press kit.)
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