SB SPACE @ ARL $ARLS015<BR>ARLS015 AO-40 "S1" Transmitter Goes Silent<P>ZCZC AS15 <BR>QST de W1AW <BR>Space Bulletin 015 ARLS015<BR>From ARRL Headquarters <BR>Newington, CT August 14, 2001<BR>To all radio amateurs<P>SB SPACE ARL ARLS015<BR>ARLS015 AO-40 ''S1'' Transmitter Goes Silent<P>AMSAT reports the 2.4 GHz ''S1'' transmitter aboard AO-40 has gone<BR>silent. Ground controller Stacey Mills, W4SM, says the transmitter<BR>abruptly quit August 13 at around 1258z while AO-40 was in view of<BR>most of the Eastern Hemisphere during orbit 362.<P>He reports normal telemetry readings up to the point that the<BR>transmitter ceased operating and that no commands were being sent or<BR>experiments under way at the time.<P>An onboard scheduler switched on the S2 transmitter at the<BR>appropriate point in the spacecraft's orbit. Mills said subsequent<BR>telemetry indicated no abnormalities or logged events to account for<BR>the failure.<P>The S1 transponder, connected to a higher-gain parabolic antenna,<BR>had been brought into the rotation to offer improved coverage when<BR>the satellite was farther away from Earth. The S2 transponder is<BR>connected to a helical antenna that has about 10 dB less gain than<BR>the parabolic antenna.<P>An initial attempt to manually switch the S1 transmitter back on did<BR>not appear successful. While ground controllers continue to study<BR>the situation, the S1 transmitter has been taken out of the<BR>schedule. The U-band and L1-band to S2-band transponder passbands<BR>will remain active from MA 10 to MA 30 and MA 44 to MA 100. The<BR>RUDAK digital transponder is connected to the S2 transmitter, and<BR>the beacon is off from MA 30 to MA 44.<P>''The schedule may also be modified for longer passband periods,<BR>given the broader coverage of the S2 helical antenna,'' Mills added.<P>For more information on AO-40, visit the AMSAT-DL Web site, <A HREF="http://www.amsat-dl.org/" TARGET=_blank>http://www.amsat-dl.org/</A> or the AMSAT-NA Web site, <A HREF="http://www.amsat.org." TARGET=_blank>http://www.amsat.org.</A> <BR>NNNN<BR>/EX