Dear All, <P>Lot's of good news about AO-40! <P>The SEU (sensor electronic unit) is triggering the sun again after the<BR>end of eclipse on orbit #147. <P>The telemetry channel #100 (analogue spin rate) is now showing a value<BR>of #49. This is the same value that it was showing on orbit #89 when we<BR>lost Sun Sensor triggering. <P>Within a few orbits we should see that the Sun Sensor SS2 also starts<BR>triggering and this would allow us to obtain attitude information and<BR>re-start magnetorquing to spin-down the spacecraft. <P>A week ago the 3-Axis sun sensors have been turned on and they seem to<BR>work nominally. It was planned to use the information from the 3-axis<BR>omni directional sun sensors to obtain the necessary reference<BR>information for a new algorithm to spin-down the spacecraft without the<BR>SEU. The new software code, which will be patched into the 20ms<BR>interrupt service, is almost ready for upload, but due to the premature<BR>return of the SEU data, this might no more be necessary. <P>Analysis of the IHU temperature by DB2OS recently revealed, that the<BR>maximum sun angle, with the lowest temperatures, was much earlier than<BR>anticipated. The temperature of the IHU reached it's minimum exactly on<BR>2001 February 01 with a temperature of about -8.4 °C. This is almost one<BR>month earlier than originally thought. There is no explanation at the<BR>moment, why this is premature. <P>The spin rate of around 17.5 RPM did not changed in the last couple of<BR>weeks and whatever it caused to increase, it stopped. As soon as the SEU<BR>will deliver good sun sensor data, the magnetorquers will be used under<BR>the control of the IHU (integrated housekeeping unit) to reduce the<BR>spin, which will than make attitude changes easier. This will also<BR>improve the telemetry reception on S-band. <P>The next milestone is to bring the spacecraft into a good orientation to<BR>fire the Arcjet with no electrical power and gaseous ammonia only. The<BR>test firing will be used to check the Arcjet control electronics and<BR>valves. Even without the Arcjet "burning", the thrust from the test<BR>firing will be enough to raise the perigee by about 100km. <P>Several independent analysis (including the french space agency CNES)<BR>confirmed, that the current orbit will be stable for many years, i.e.<BR>more than the anticipated lifetime of the spacecraft. <P>The test firing should give us additional safety margin and a better<BR>feeling. However, it is later planned to optimize the current orbit with<BR>a full running Arcjet. This is planned after testing of the 3-axis<BR>momentum wheels, which will be used to re-orient the the spacecraft<BR>during these maneuvers. <P>While the spacecraft was in hibernation, the command stations were<BR>restless with preparations for the next activities, watching the <BR>spacecraft telemetry and healthy.<P>AMSAT-DL expresses his thanks to Paul Willmott, VP9MU for his outstanding <BR>service in gathering and archiving the AO-40 telemetry from the different <BR>parts of the world. This is vital additional information for the command<BR>stations in their continuing effort to turn P3-D back into operation. <BR>Everyone should be encouraged to send captured telemetry (with P3T) to<BR>the AO40 telemetry archive at 'ao40-archive@amsat.org'<P>After all, the spacecraft seems to be in very good shape, with no further <BR>damages or other problems detected. The power budget is very good and even<BR>during the maximum sun angle it was not necessary to reduce power<BR>consumption by turning off the S-band transmitter for parts of the<BR>orbit. <P>This is indeed a good sign for the next activities. <P>Stay tuned.. <P>Additional information can be found at the AO-40 web page at: <P><A HREF="http://www.amsat-dl.org/" TARGET=_blank>http://www.amsat-dl.org/</A><P>73s Peter, DB2OS<BR> AMSAT-DL<BR>