AMSAT-NAAMSAT News Service

July 15, 2001

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AO-40 Update

AO-40 command station W4SM recently answered many questions in an attempt to clear up any misconceptions concerning AO-40 operations in recent weeks, centered around the ATOS system and the arcjet cold firing. ANS has summarized this information:

* The old orbit was stable before any recent interaction, however, perigee was very close (in some simulations as close as 160 km). There was considerable drag at perigee, which continuously changed the mean motion and probably contributed to the perturbation in ALON (the mystery effect). Orbital tracking elements had to be frequently updated. The rapidity of the perigee flyby also made magnetorquing very tricky. To improve these things command stations attempted to raise the perigee height with the decision to cold fire the arcjet.

* The command software controlling the arcjet was not faulty and there is not any telemetry evidence to suggest any software error problems.

* The entire amount of ammonia aboard the satellite has been used and it appears the TMFC (thermal mass flow controller) failed, passing far more gas than it should have. As this was happening there was no indication of this in the received telemetry. It is quite possible that there was a slow leak in the ammonia tanks and if (in fact) there was a slow leak, it is very fortunate we did not wait any longer to use the remaining fuel. In addition, there is no evidence that the ammonia problem was due to a command error.

* The command team is now looking at what is next for AO-40. The momentum wheels have not yet been tested and the decision to deploy (or not deploy) the solar panels is under investigation. The primary goal remains to get AO-40 back into an orientation where the transponders can be operational and RUDAK testing can be completed.

* AO-40 is in a stable orbit for much more than the next 20 years as perigee is oscillating in a safe range between 810 and 1260 km.

* The aux battery is a nickel metal hydride (NiMH) battery. It is currently off of trickle charge. These cells are quite happy fully discharged and we believe that the battery will last longer if we do not keep it on trickle charge (as we have no immediate need for it, we have left it uncharged for now to prolong its life).

AO-40 is currently at approximately ALON/ALAT 311/5, accounting for the much-improved telemetry signals on the first portion of the orbit. We are torquing to approximately 320/0 (at which point the solar angle will be close to 45 degrees) and the solar sensor may stop triggering, thereby stopping the process. If this does occur, it is a benign condition because the Sun is moving away from us at almost 1 deg/day and very quickly the solar angle will be re-established.

However, we will have to wait until the end of August to be able to move all the way back to 0/0. In the mean time, when we reach ~320/0 we will stop magnetorquing and take pictures to verify our position.

Remember that there are still a number of items to check out. In particular, we may have some days of limited or no transponder activity, and even no beacon activity, while the RUDAK team uploads software and checks out some of the RUDAK functions.

The AMSAT-DL web site is currently featuring an AO-40 status summary format at http://www.amsat-dl.org/journal/adlj-p3d.htm

Stay tuned to ANS, the official source of AO-40 information.

[ANS thanks AMSAT-NA and AMSAT-DL for this information]

AMSAT-UK Colloquium

The 16th AMSAT-UK Colloquium will be held at Surrey University, Guildford, Surrey, United Kingdom, July 27 - 29, 2001.

In addition to the standard program, additional attractions include a satellite beginners session on Friday afternoon and tours of the Surrey University satellite facilities. Microwave equipment testing, including 2.4GHz antenna gain testing, will be available. Also, the competition for a new logo for the AMSAT OSCAR 40 satellite will take place at the Colloquium, with winners to be announced.

Full details of the event are at http://www.uk.amsat.org/colloquium.htm

The provisional program is on the AMSAT-UK web site, see http://www.uk.amsat.org/colloquium/program.htm

[ANS thanks Richard Limebear, G3RWL, for this information]

STS-104 Mission Underway

The Space Shuttle Atlantis lifted off on time last week, and, after a smooth climb to orbit, was quickly enroute to deliver a new doorway to space to the International Space Station.

Atlantis Commander Steve Lindsey, Pilot Charlie Hobaugh and Mission Specialists Janet Kavandi, Jim Reilly and Mike Gernhardt will install an airlock named Quest on the station, increasing the orbiting complex's onboard capabilities for maintenance and construction and completing a major milestone in the station's orbital construction. The new airlock will enable station crews to perform space walks in U.S. space suits without the shuttle being present. This ability will enhance the station's capabilities for maintenance and construction and complete a major milestone in the station's orbital construction.

Commander Lindsey smoothly docked the space shuttle with the International Space Station late Friday about 240 statute miles above the northeastern coast of South America. With both spacecraft moving at about 17,500 mph, Lindsay moved Atlantis to the station at a relative speed of about a tenth of a foot per second.

The five-member crew of Atlantis spent their fifth day in space working with the Expedition-2 crew aboard the International Space Station to continue the activation of the station's new airlock, including:

In addition to checking and activating Quest's systems, the crews removed the motor controllers from the airlock's berthing mechanism, which are no longer needed now that the airlock is firmly attached to the station.

After the airlock was attached to the station early Sunday morning, and the first part of its checkout was completed, the shuttle and station crews held a ribbon cutting for the new addition.

STS-104 Commander Lindsey and Pilot Charlie Hobaugh fired the shuttle's engines for an hour Sunday night to boost the station to an altitude of 238 by 235 statute miles (383 by 375 kilometers). Mission Specialists Michael Gernhardt, Janet Kavandi and Jim Reilly also worked on equipment and supply transfers between the shuttle and station.

The ARISS team reminds all that the ISS crews will be very busy during the STS-104 mission (so voice operations may change tempo). In addition, the amateur radio gear may need to be turned off for extended periods for the safety of the ISS, shuttle, and their crews.

[ANS thanks NASA and ARISS for this information]

ANS in Brief

ANS news in brief this week includes the following:

Weekly Satellite Report

Link to the weekly report on satellite ...

All Satellites
ISS . RS-12 . RS-13 . RS-15 . AO-10 . UO-11 . UO-14 . AO-16 . DO-17 . WO-18 . LO-19 . FO-20 . UO-22 . KO-23 . KO-25 . IO-26 . AO-27 . FO-29 . TO-31 . GO-32 . SO-33 . PO-34 . SO-35 . UO-36 . AO-40 . SO-41 . SO-42


Please send any amateur satellite news or reports to the ANS Editors at ans-editor@amsat.org, or to ANS Editor Dan James, NN0DJ, at nn0dj@amsat.org.

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This week's AMSAT News Service bulletins were edited by AMSAT  News Service editor Dan James, NN0DJ.

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