This week marks two months and a half that QuakeSat has been in orbit. QuakeSat continues to work very well. The orbit has precessed so that the satellite is in the sun 100% of the time. Temperatures have climbed a few degrees with the maximums for the CPU and 5 volt power supply climimbing to 145 -150 deg F range, far enough from the 185 deg limit.
The CPU has had several "upsets" over the last few weeks. Some of the problems we think were due to an interrupt contention which caused the counters to stop being serviced (translation----the satellite stops taking data). Several others upsets may have been caused by high energy particles disturbing computer instructions and locking up the computer. The "Watchdog Timer", a separate PIC processor, worked great, detected the lack of a CPU "heartbeat", and reset the computer. This cuases the clock to reset to zero, so we must reset the clock to synchronize GMT to the CPU clock before starting to take data again. We lose a bit of data , but this is not a big problem, and we have the process refined now.
Satellite clock timing is being refined by analysis of transmitted commands and --believe it or not-- by detection of lightning along the east coast of US as seen by the magnetometer. These lightning strikes are detected, located, and timed to GMT by a series of ground sensors all over the US. We see the pattern on the ground and match them to the pattern in the magnetometer data, and when the signals are clear enough--we can get our clock timing down to under 1 sec uncertainty. Thanks to our analyst King Lear and professor Inan at Stanford for that capability.
As to what we have seen in the data----- There are MANY signals present---just sorting through them is a major effort. There were many noise signals in the original data because the magnetometer is so sensitive, it picks up EVERYTHING--including subtle thing inside the spacecraft!
For example, we have identified and eliminated noise from the QuakeSat's 10 sec beacon signals during magnetometer collections, the 1/sec CPU heartbeat, and the 10/sec CPU process interrupt noise--thanks to the analysis by Paul Clarke and the satellite reprogramming by Louis DiMartini The radio modem injects a 600 and 1200 Hz signal in the 1000Hz magnetometer channel, but these are clear signals and can be eliminated with post-processing digital filters (or ignored).
We have seen lightning, the effects of lightning called whistlers, and (we think) auroral noise near the earth's poles. We have seen some strange tones (probably man-made) at 84 Hz and several other other tones that may be BMEWS radar signatures (tbd).
We have been collecting large amounts of data over historically active, worldwide earthquake areas to get "background" data before future quakes. We also have been "chasing" recent large quakes to see if there are "residual ELF signals" after the quakes. We are currently trying to see if a "double bump" seen over a M7.2 earthquake in southern New Zealand could be such an ELF earthquake signature. This is going to be a long process to coax the subtle signals out of the raw data. We then need to compare non-earthquake passes with earthquake passes to demonstrate a change exists.
The objective now is to get as much data out of the satellite as possible before cosmic radiation kills it. Scott Flagg has been refining the tasking commanding scripts. Louis DiMartini has been refining the command and control process interface with the satellite CPU. John Doering has been investigating if we can improve the performance of the Terminal Node Controller (TNC) to get more data. Jim Lemon has been updating the telemetry system (TAPS) to add many features needed by this packet system. All this to coax more data out of the satellite.
By the way, we have gotten 25-30 MB of data, all of which Lew Franklin, Paul Clark and Clark Dunson have been sorting, reviewing, and analyzing as fast as they can.
The team is doing great things. The satellite is working well. We are trying to keep up with the flood of data--and trying to get more (maybe with another telemetry site in Alaska---tbd).