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Astromag FF



Astromag Free-Flyer (FF) permits measurements of high energy (>1GeV/nucleon) cosmic ray nuclei and electrons with unprecedented accuracy and sensitivity. The primary science objectives for Astromag FF are: to test cosmological models by searching for antimatter and dark matter candidates; to measure the high energy spectra of antiprotons and protons; to study the origin and evolution of matter in the galaxy by direct sampling of galactic material for evidence of nucleosynthesis and galactic evolutionary effects; to study the origin and acceleration of the relativistic particle plasma in the galaxy and its effects on the dynamics and evolution of the galaxy; and to measure the isotopic composition of cosmic ray nuclei at energies of several GeV/nucleon and with previously unattained sensitivity. In 1988, Astromag was originally designed to be one facility on the Space Station Freedom (SSF), and experiments were selected in 1989. In late 1990, it became clear that facilities the size and scope of Astromag could not be accommodated on a reduced-scale SSF, so an Astromag Free-Flyer concept was developed and proposed in May 1991. In June 1991, the Space Science and Applications Advisory Committee moved Astromag FF from first to fifth in the OSSA queue of missions for the 1990's, and therefore it is not currently funded and it will not be launched before about 2005, if ever. Astromag FF consists of: a magnet of two identical 1.44-m diameter magnet coils of superconducting NbTi wire, with a 1.67-m separation; surrounded by a 2250 liter liquid helium dewar in the spacecraft's central section; with a scientific experiment (LISA or WiZard) on each end; plus the primary power, attitude control, and communications sub-systems, etc. The magnetic coils are about 10-cm long, and a few centimeters thick. Their detailed structure is not yet decided. The coil axes are colinear with each other and with the spacecraft longitudinal axis, and the spacecraft experiments are attached to the central section at the ends of this axis. The magnet uses a design current of about 800 A and the peak field at each coil is approximately 7 T, but decreases rapidly with distance from the coil. To make the dipole moment as low as possible, the coils have opposite polarity. (So when the coils are powered to 800 A, the force pushing the two coils apart is just over 35 metric tons.) Since the coils are superconducting, the circulating current decays less than 1% per year, so that the magnetic field is maintained without a need for continuous application of power. The spacecraft is planned to be in a low (500 km altitude) circular geocentric orbit, and the mission lifetime is expected to be 2 years. The attitude control system must provide time-tagged attitude knowledge to 1 or 2 degrees accuracy for each axis, and give a pointing control accuracy of 10 degrees about each axis. The attitude knowledge is provided by two earth horizon scanners and a 3-axis magnetometer on a 50-foot boom, plus sun sensors. The pointing control is done with a pitch wheel momentum-biased system using magnetic torquers for initial acquisition, wheel momentum unloading, spacecraft nutation damping, and roll/yaw control. The power supply system, composed of two solar panels, with areas of approximately 15 sq m, and two 50-Ahr NiCd batteries, for use during spacecraft eclipses, provides the required 1250 W orbital average power at +28 V, and the 2500 W for initial magnet charging. During full sun periods with fully charged batteries, approximately 2880 W is expected to be available. The command and data handling system is based on the Small Explorer Data System and it provides an orbital average telemetry data stream of 100 kbps and the capability for its on-board storage in 2.5 Gbits of bulk memory, real-time WiZard diagnostic data at 250 kbps, and stored and real-time command processing for either 1 or 2 kbps rates, plus an additional 1.25 Mbps high speed serial port for stored data dumps. The RF communications system consists of NASA Standard Transponders, power amplifier, 28 dB high-gain pointable S-band antenna, omnidirectional antennas, and electronics. It performs stored data dumps at up to 2 Mbps through the Tracking and Data Relay Satellite System for about 21.8 minutes every six hours, 1kbps telemetry and command communications, and real-time data transmission at 250 kbps (for WiZard diagnostic data). The best reference for details and descriptions of Astromag FF and its experiments is the document, Astromag Free-Flyer, Vols. I and II, May 1991, done at GSFC which provides the results of the Astromag FF program study and recommendations. It is available through the project personnel.

Alternate Names

  • Astromag Free-Flyer
  • SS/Astromag

Facts in Brief

Launch Date: 2005-01-01
Launch Vehicle: Atlas
Launch Site: Cape Canaveral, United States
Mass: 5250.0 kg

Funding Agency

  • NASA-Office of Space Science (United States)


  • Astronomy

Additional Information

Questions or comments about this spacecraft can be directed to: Coordinated Request and User Support Office.



NameRoleOriginal AffiliationE-mail
Dr. Robert GoldenGeneral ContactNASA Johnson Space Center 
Dr. Robert E. StreitmatterGeneral ContactNASA Goddard Space Flight
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