Friday, November 21, 2014 marked the one year anniversary of the launch of $50SAT/MO-76 PocketQube satellite.
Michael Kirkhart KD8QBA writes:
Our little creation was launched from Dombarovsky Air Base in Russia at 07:01 UT (which was 2:01 AM here in EN82 land) as one of 33 satellites aboard a Dnepr rocket. It was first heard by Jan, PE0SAT, at 08:46 UT, and by Stuart GW7HPW at 09:17 UT, and has been operating continuously ever since!
The $50SAT/MO-76 Dropbox now contains a snapshot of all the telemetry gathered from launch day through November 21, 2014.
$50SAT/MO-76 continues to operate normally, but the battery capacity has been slowly dropping to the point where it barely registers above 3500 mV when passing over EN82 land during daytime (decending) passes. I have been able to capture telemetry while it passes over Anton’s (ZR6AIC) WebSDR station http://zr6aic.giga.co.za:8902/ which is located in South Africa. During ascending passes, which occur between 20:00 and 21:30 UT, $50SAT/MO-76 has just transitioned from being in sunlight to being in eclipse, and the battery voltage is between 3602 and 3642 mV.
Over the life of $50SAT/MO-76, we have observed the following:
The maximum battery voltage was 3824 mV, while the minimum was 3440 mV
The maximum PCB temperature was 25 degrees C, while the minimum was -29 degrees C
The maximum RFM22 temperature was 29 degrees C, while the minimum was -30 degrees C
The maximum MPPT (solar) power was 312.84 mW
The maximum idle (RFM22 off) current was 3 mA, while the minimum was 2 mA
The maximum receive mode current was 31 mA, while the minimum was 21 mA
The maximum transmit mode current was 88 mA, while the minimum was 77 mA
On December 4, 2013, the folks at NORAD and Celestrak (with help from Mike, DK3WN) were able to identify $50SAT/MO-76 as object 2013-066W. At this time, apogee was at 640 km, and perigee was 595 km. As of November 21, 2014, apogee is at 599 km, and perigee is at 565 km. This means the average altitude has decreased by about 36 km. A spreadsheet, along with a graph of the orbital data is available on the $50SAT/MO-76 Dropbox
While we did not have time to demonstrate this at the AMSAT-NA Space Symposium, we now have a working Arduino/RFM22 based groundstation. It utilizes a slightly modified version of the Sparkfun RFM22 Arduino shield https://www.sparkfun.com/products/11018 Additional information, including photos, marked up schematics, and the Arduino sketches, is available (guess where?) on the $50SAT/MO-76 Dropbox.
In addition to the original, receive-only sketch (S50SAT_receiver), there is a new version (S50SAT-Groundstation) which includes transmit capability, which supports all three open uplink commands. Both versions are capable of receiving all GFSK based packets, including the FEC packets.
I have successfully received $50SAT info and FEC packets from about 1200 km slant range with my groundstation using an Advanced Receiver Research P432VDG LNA http://advancedreceiver.com/page5.html with my homebrew 6 element WA5VJB yagi. The LNA is needed to improve the sensitivity of the RFM22, which is about -99 dBm. Since the RFM22 can only output 20 dBm (100 mW) and the minimum EIRP needed to uplink to $50SAT/MO-76 when it is directly overhead is about 36 dBm (4W), either a 16 dB gain antenna, an external linear amplifier, or both will be needed to successfully uplink.
Speaking of uplinking, no one has completed the $50SAT/MO-76 Uplink Challenge. This challenge is open to any licensed amateur radio operator, and the prize for successful completion is (drum roll…) a certificate of technical achievement, signed by all three of the $50SAT/MO-76 developers.
Our thanks to all who has supported us in this project, including all of you telemetry gathers. Please keep the telemetry coming!
Michael Kirkhart KD8QBA
$50SAT was a collaborative education project between Professor Bob Twiggs, KE6QMD, Morehead State University and three other radio amateurs, Howie DeFelice, AB2S, Michael Kirkhart, KD8QBA, and Stuart Robinson, GW7HPW. The transmitter power is just 100 mW on 437.505 MHz (+/-9 kHz Doppler shift) FM CW/RTTY. $50SAT uses the low cost Hope RFM22B single chip radio and PICAXE 40X2 processor.
There is a discussion group for $50SAT http://groups.yahoo.com/groups/50dollarsat/