ZCZC AS04 QST de W1AW Space Bulletin 004 ARLS004 >From ARRL Headquarters Newington, CT February 6, 2001 To all radio amateurs
SB SPACE ARL ARLS004 ARLS004 AO-40 Future Rests on Reducing Spin, Regaining Attitude Control
The key to a successful AO-40 recovery effort continues to be a matter of reducing the satellite's spin and regaining the ability to adjust its attitude from the ground. ''The current problem is the lack of accurate AO-40 attitude data,'' AMSAT News Service said. Accurate data are not available because AO-40's sun sensor is not seeing the sun because of the satellite's attitude.
Only when ground controllers can accurately determine the satellite's attitude will it be possible to change it and correctly aim AO-40's high-gain antennas for optimal reception on Earth--and that's assuming the transmitters are functioning on bands other than 2.4 GHz. Ground controllers have had no luck hearing AO-40's transmitters on the omnidirectional antennas on 2 meters, 70 cm or 1.2 GHz. Since the satellite's computer was reset and telemetry resumed December 25, the AO-40 ground team has been analyzing telemetry sent via the 2.4 GHz beacon--the only transmitter now operating.
AMSAT-Germany described AO-40 as ''in the fog'' because its high angle with respect to the sun temporarily prevents the sun sensors from providing attitude data.
Ground controllers have been pinning their hopes on a previously announced ''de-spinner'' programming routine that would permit AO-40 spin control without having to rely on the sun sensors. The satellite's current spin rate is reported to be 17.7 RPM. But even if the programming fix fails, ''it's no cause for panic,'' AMSAT-DL said. By April, controllers reason, the satellites sensors will again see the sun and ''thanks to magnetorquing, spin and attitude can be actively improved upon the rising tide.'' Once the spin is reduced, sun angle improved, and antennas pointed, testing can resume. Still outstanding are tests of the VHF and UHF transmitters, the arc-jet motor, and the reaction wheels, among others.
Both AMSAT-DL President and AO-40 Project Leader Karl Meinzer, DJ4ZC, and AMSAT-NA President Robin Haighton, VE3FRH, have continued to be optimistic that AO-40 will have a useful life of Amateur Radio service. Command stations James Miller, G3RUH, Stacey Mills, W4SM, made a long-term prediction of AO-40's new orbit. They say that even after last year's incident--which silenced the satellite for nearly two weeks--and the resulting decrease of perigee, AO-40's orbit will be stable, although perigee will oscillate by several hundred kilometers.
AMSAT-DL says the recovery effort has been slowed somewhat because of limited access time on the part of the command team, due to AO-40's current orbital parameters.
Discussions of the future of AO-40 are expected to dominate the eighth AMSAT-DL Symposium on March 17, AMSAT-DL said. NNNN /EX
* Origin: ---=== RA9LO Station at MO27SC ===--- (2:5077/39) __________________________________________________________________
Alexander
RZ6HGG Stavropol E-mail:rz6hgg@skiftel.ru FidoNet: 2:5064/11.30 9 февраля 2001 г. 10:06:44
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