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--></style></head><body lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal"><span style="color:#1f497d">PCSAT (NO44) is again returned to users (but not usable until a few weeks when sun angles get better). The Transponder on ISS is also operational now.</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">The variation of power available to PCSAT is inversely proportional to the “sun-to-orbitplane-angle” (viewable in Instantrack with the “E” and “D” keys. It is currently above 78 degrees. Once it went above about 65 degrees was our last successful commanding. </span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">Recovery did not work this period. But we learned enough to be more successful in the Fall.</span></p><p class="MsoNormal">
<span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">A “sun-to-orbitplane-angle” means PCsat’s orbit is now over the day/night terminator meaning it is in full sun (no eclipses) with solar power coming in on the (weaker) side panels and little if any on the +Z face(best panel). Attitude is maintained by alignment with the Earth’s magnetic field. It’s the best time for a recovery (no eclipses to cause a reset), but the worst time for commanding. It is too weak to respond to the needed logon and 3 additional commands. Though it will be strong again as the sun angle improves (lower).</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">Then it will have better sun on the +Z face for commanding, but then it will be doing Eclipses. And even though we can then command it to turn off unnecessary loads, it does not have enough time before the next eclipse to charge up enough to survive the next eclipse.</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">What we did (re)learn is a condensed command method where we can put all 3 PCSAT low-power commands in a single packet (using the TNC’s ^V pass character). That way, we only need a successful logon to complete the Restoration. 1) The CONNECT ACK. 2) The password challenge, 3) Then the command prompt. Then we can hit it with the full low-power command set and disconnect all in one packet which cancels the need for PCSAT to respond to each command separately.</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">On the FIRST day available in full sun(our best shot), I not only got logged on, but completed all 3 requried functions. Then signals sounded so good, I got greedy and put in the another three (which also improves power budget, but not as much as the first three). Yep, I gambled and lost. It died on the last one! The next day I got all 3 in, and it died on the 3<sup>rd</sup> command due to a user packet I think. Days since, I have been unable to logon. Hence, end of this attempt period.</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">In most attempts in the past (after successful logon) we would send one command at a time to give it a few seconds rest between each one. But these 3 commands then required 3 ACKS and 3 RESPONSES in addition to the 3 required to get logged. Those extra 6 packets kill it, especially if there was a user packet in there. Next time all we need are the 3 loggon responses.</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">Also, next time, we will give users advance warning to QRT all transmissions when we are trying to command. Each one of their packets robs us of power we need to complete the command. I failed to warn everyone this time, and so we had some interference.</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">As sun angle improves, You may continue to experiment with PCSAT during MIDDAY passes. That is when it is strongest (in the Northern Hemisphere), but do limit yourself to only attended operations so humans can actually contact humans, or if you are doing an unattended test, keep your transmissions to once every 2 minutes. That should let you get one good successful packet per pass. Which is the mission of PCSAT. </span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">See the downlink on <a href="http://pcsat.aprs.org">http://pcsat.aprs.org</a></span></p><p class="MsoNormal"><span style="color:#1f497d"> </span></p>
<p class="MsoNormal"><span style="color:#1f497d">There you can see the telemetry packets (list at the bottom of page) right now are rarely getting above 001 meaning typically a minute or so of life before it gets overloaded and resets back to 000.</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">It is easy to visualize the relationship of the sun angle to the orbit plane and to see how that affects power budget given that our best panel (out of 5) is on the +Z face and that is magnetically aligned to point towards magnetic South. There is NO panel on the –Z which is why PCsat is rarely usable in the Southern Hemisphere (not planned, but just a result of it crashing in every eclipse).</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">Just thought you would like to know what is going on with one of the oldest student projects in space that is still “semi-operational” for users.</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d">Bob, Wb4APR</span></p><p class="MsoNormal"><span style="color:#1f497d">US Naval Academy Satellite Lab</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p><p class="MsoNormal"><span style="color:#1f497d"> </span></p><div><div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0in 0in 0in"><p class="MsoNormal">
<b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Robert Bruninga [mailto:<a href="mailto:bruninga@usna.edu">bruninga@usna.edu</a>] <br>
<b>Sent:</b> Thursday, January 31, 2013 10:53 AM<br><b>To:</b> <a href="mailto:amsat-bb@amsat.org">amsat-bb@amsat.org</a><br><b>Cc:</b> <a href="mailto:aprssig@tapr.org">aprssig@tapr.org</a>; <a href="mailto:aprs@yahoogroups.com">aprs@yahoogroups.com</a>; <a href="mailto:bruninga@usna.edu">bruninga@usna.edu</a><br>
<b>Subject:</b> QRT all PCSAT transmissions!</span></p></div></div><p class="MsoNormal"> </p><p class="MsoNormal">Please QRT all transmissions to PCsat to save power for COMMANDing.</p><p class="MsoNormal"> </p><p class="MsoNormal">
PCSAT (W3ADO-1) is entering its 3 day RECOVERY window this year starting 31 Jan.</p><p class="MsoNormal"> </p><p class="MsoNormal">Today we got logged on for commanding twice, but both times user packets killed the bird. </p>
<p class="MsoNormal"> </p><p class="MsoNormal">At best PCSAT can usually only save up enough power for 2 or 3 solid packets per pass and we need 3 successfully for command and recover. One user packet in the middle of that and we lose it for the pass.</p>
<p class="MsoNormal"> </p><p class="MsoNormal">MY fault for not making this announcement earlier. Not their fault. But if you see this email and you are transmitting to PCsat, please QRT for the next several days.</p><p class="MsoNormal">
</p><p class="MsoNormal">Commanding is being done from the East and West coast of the USA and over Germany.</p><p class="MsoNormal"> </p><p class="MsoNormal">WB4APR, Bob</p><p class="MsoNormal">USNA Command Station</p><p class="MsoNormal">
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