INTRODUCTION AND MISSION OBJECTIVES

THE PROGRAM

The CRRES program is a joint NASA and Department of Defense (DOD) undertaking. The DOD portion of the program is managed by the Air Force Space Division's Space Test and Transportation Program office. The NASA portion is managed by Marshall Space Flight Center. The DOD provides the experiment instrumentation and spacecraft funding. NASA provides integration and launch by the Atlas I, as well as a portion of the experiment funding. The Atlas I is being procured by NASA's Lewis Research Center. The spacecraft and its payload adapter are being designed, built, and tested by Ball Space Systems Division (BSSD) under NASA/MSFC contract NASB-34025. The system will be ready for launch in May of 1990.

The spacecraft was originally built for launch by the Space Transportation System (STS), but has been modified for launch by the Atlas I vehicle. These modifications included the removal of a large orbit transfer stage (with a modified Solid Spinning Upper Stage-A) and removal of one-half of the original chemical canister payload. The STS cradle was replaced with a payload adapter to mate with the Centaur upper stage of the Atlas I, and the solar panels were relocated to fit into the 14-foot diameter Atlas I fairing.

MISSION OBJECTIVES

The spacecraft operates in a highly elliptical geosynchronous transfer orbit (GTO) with an initial perigee of 350 kilometers altitude and an apogee at geosynchronous altitude of 35,786 kilometers. Operations in this orbit support both NASA and DOD scientific experimental objectives. There are three major objectives: 1) NASA performance of active chemical release experiments in the ionosphere and magnetosphere, 2) DOD studies of the natural radiation environment and studies of the effects of this radiation environment upon microelectronic components as CRRES travels through the inner and outer radiation belts of the earth, and 3) DOD low altitude studies of ionospheric irregularities which are performed in the ionosphere near the orbit perigee.

NASA CHEMICAL RELEASE EXPERIMENTS

CRRES will carry a complement of chemical release canisters which will be released at certain times over ground observation sites and diagnostic facilities. These releases form large clouds about 100 kilometers in diameter that will interact with the ionospheric and magnetospheric plasma and the earth's magnetic field. These interactions will be studied with optical, radar, and plasma wave and particle instruments from the ground, aircraft and the CRRES spacecraft. Those controlled experiments which are performed near perigee will further the understanding of the interaction of plasmas with magnetic fields, the coupling of the upper atmosphere with the ionosphere, the structure and chemistry of the ionosphere, and the structure of low-altitude electric fields. Those which are performed near apogee in the earth's magnetosphere will study the formation of diamagnetic cavities, coupling between the magnetosphere and ionosphere, and the effects of artificial plasma injections upon the stability of the trapped particles in the radiation belts. The chemical release experiments and associated ground and airborne diagnostics were selected by the NASA Announcement of Opportunity process. A CRRES Investigators Working Group has been formed, and the investigators divided into teams based on mutual scientific interests and the ability to make coordinated multipoint observations. Because some of the original chemical canisters were removed from the CRRES-GTO satellite, plans have been made to supplement the remaining CRRES releases with some by sounding rockets, a Pegasus-launched vehicle, and other ELV-launched vehicles in order to meet the originally selected scientific objectives. The sounding rockets will be launched over Kwajelein and Puerto Rico. The Puerto Rican releases will be at approximately the same time as the CRRES-GTO perigee releases so they can be observed during a single campaign.

The Chemical Release Teams are:

Team 1 - Electric Fields and Ion Transport
The study of low-latitude electric fields and the transport of ions along magnetic field lines to the conjugate ionosphere.

Team 2 - Ionospheric Modifications/Plasma Processes
Artificial creation of ionospheric perturbations and production of ionospheric irregularities. Study of momentum coupling from injected plasmas and the background ionosphere. Testing of the critical ionization hypothesis by injection of neutral atoms at orbital velocities. Comparison of observed behavior of injected plasma with computer models.

Team 3 - Large-Scale Plasma Processes/Equatorial Triggering
Large-scale releases of chemicals to produce ionospheric density depletions to stimulate ionospheric irregularity formation. Creation of ionospheric holes to study the effects upon high4requency wave propagation. These releases will be done with sounding rockets.

Team 4 - High Altitude Releases
Effects of artificial plasma seeding of the magnetosphere. This team will work in conjunction with the DOD particle and wave investigators. Ground-based optical and radar diagnostics will observe large-scale phenomenon, while in-situ CRRES measurements will examine localized microscale effects. The CRRES instruments will also determine the state of the magnetosphere, providing valuable data to allow the determination of optimal conditions for releases.

DOD STUDIES OF THE RADIATION BELTS AND THEIR EFFECTS

The primary focus of these studies is on the natural radiation environment and the effects of this environment on microelectronic components. CRRES will travel through the inner and outer radiation belts of the earth. The latest microelectronic components will be carried onboard CRRES and be exposed to this radiation environment to establish their capabilities for use in future space missions. Also, the radiation belts will be accurately measured so a direct correlation can be made between the exposure and microelectronics performance. More than 40 instruments will be operating, including an experimental new generation of high efficiency solar panels and instruments which are investigating the effects of solar flares and cosmic rays on the earth's magnetosphere and radiation belts.

The experiments are:

1. High Efficiency Solar Panel (HESP) - an experiment designed to determine the performance of GaAs solar panels under the effects of the natural radiation environment and under ambient and heated conditions.
2. Spacerad - Consists of some 30 instruments which expose microelectronics to the space radiation environment, measure the ambient environment including magnetic and electric fields, plasma, particles, waves, and total radiation dose. Spacerad includes 2 pairs of long wire booms that extend up to 50 meters from the spacecraft.
3. Solar Flare Isotopes experiment - Measures cosmic ray particles and heavy ion composition in the magnetosphere.
4. Heavy Ions experiment - Measures the intensity, energy and pitch angles of low, medium and high energy ambient ions.

DOD LOW ALTITUDE SCIENTIFIC STUDIES OF IONOSPHERIC IRREGULARITIES

This set of observations will be made near the the perigee of selected CRRES orbits and in support of the chemical releases. They will study naturally-occurring and artificially produced ionospheric perturbations and the effects of ionospheric perturbations upon communications paths. The onboard set of instruments consists of two pulsed plasma probes, a very low frequency wave analyzer including two electric field antennas and a magnetic field loop antenna, and a quadrupole ion mass spectrometer.