Video of $50SAT ham radio satellite talk

Yaesu handheld and $50SAT 1.5U PocketQube

Yaesu handheld and $50SAT 1.5U PocketQube

The story behind $50SAT, a new approach to amateur satellite design which became the world’s smallest operational satellite, built for £125 in a garden shed.

On Saturday, August 6, Stuart Robinson GW7HPW gave a presentation on the amateur radio satellite $50SAT to the Electromagnetic Field event EMF 2016 in Guildford.

Talk Description: If you are building an Amateur satellite the simple choice would be to assemble a device with all the latest satisfyingly advanced and complex tech. The $50SAT team made a decision to go against convention and produce a design with the minimum of components.

$50SAT was the first of a new class of satellite pioneered by Professor Bob Twiggs KE6QMD; the PocketQubes, designed to be small and light so they would be cheap to launch. $50SAT was launched in November 2013 using a Dnepr rocket from Dombarovsky Air Base in Russia and remained working in orbit for 20 months, the team had only expected it to last for a month at best.

Watch The story behind $50SAT

$50SAT http://www.50dollarsat.info/

$50Sat Eagle2 PocketQube
https://amsat-uk.org/2013/11/22/50sat-eagle2-pocketqube-operational/

$50SAT Falls Silent  http://www.dk3wn.info/p/?cat=143

ISS Astronauts Link-Up with ITU WRC-15 in Geneva

ARISS contact between 4U1WRC and OR4ISS November 3, 2015

ARISS contact between 4U1WRC and OR4ISS November 3, 2015

The ITU World Radiocommunication Conference 2015 (WRC-15) is taking place in Geneva from November 2-27. On Tuesday, November 3 at 1241 UT there was an amateur radio link-up between WRC-15 and two astronauts on the International Space Station (ISS).

The contact took place using the permanent amateur radio station at the ITU. The station’s normal call sign is 4U1ITU but during the conference the special call sign 4U1WRC is being used.

Students from Institut Florimont were able to use the ITU station to talk to astronauts Kjell Lindgren KO5MOS and Kimiya Yui KG5BPH who were using the  amateur radio station in the ISS Columbus module, call sign OR4ISS.

The Amateur Radio on the International Space Station (ARISS) program established the first permanent amateur radio presence in space 15 years ago. The inaugural ARISS contact took place on December 21, 2000, between a member of the ISS Expedition 1 crew and youngsters at Luther Burbank Elementary School near Chicago. Several pupils and a teacher got to chat using amateur radio with “Space Station Alpha” Commander William “Shep” Shepherd KD5GSL.

Watch ARISS contact with WRC-15 and Institut Florimont

The ARISS program lets students worldwide experience the excitement of talking directly with crew members of the International Space Station, inspiring them to pursue interests in careers in science, technology, engineering and math, and engaging them with radio science technology through amateur radio.

ARISS http://ariss-eu.org/

ARISS Celebrates 1000th Event, 15 Years of Permanent Ham Radio Presence in Space
http://www.arrl.org/news/view/ariss-celebrates-1000th-event-15-years-of-permanent-ham-radio-presence-in-space

RSGB WRC-15 information http://rsgb.org/wrc-15

$50SAT Falls Silent

Yaesu handheld and $50SAT 1.5U PocketQube

Yaesu handheld and $50SAT 1.5U PocketQube

The $50SAT amateur radio spacecraft ,which measures just 5x5x7.5 cm and weighs only 210 grams, has ceased transmitting after nearly 20 months in space.

Michael Kirkhart, KD8QBA, writes:

Tuesday, July 21, 2015 marked the 20 month anniversary of the launch of $50SAT/MO-76/Eagle2, and unfortunately, it appears to have gone silent.  The last time I heard it was on Sunday, July 19, 2015, 08:42 UTC from Anton’s (ZR6AIC) WebSDR.  A screenshot of the WebSDR while $50SAT was transmitting RTTY, a screenshot of gpredict showing its location during the transmission, and the captured RTTY audio are up on the Dropbox; they are accessible via the following URL:

https://www.dropbox.com/sh/l3919wtfiywk2gf/AAD6Q3gJYziGVwavQ1OkSxAia/Latest-Observation

Unfortunately, there was a fade starting in the middle of the capture, so I was only able to do a partial decode:
2015-07-19,08:42,KG43,ZR6AIC/KD8QBA,$50SAT,,2990,15719,,,84,3,,22,?,?,?,?,?,?,*? (NO CHECKSUM – MISSING DATA)

Has anyone else has heard $50SAT since July 19?  If so, please let us know.

The likely cause of failure was a near complete loss of solar power.  Looking at the last 5 complete RTTY telemetry messages, the amount of solar power being generated was very low:

2015-06-21,08:23,KG43,ZR6AIC/KD8QBA,$50SAT,,2990,15688,,,82,3,,22,16,78,,3435,1572,3319,*4A  (3435 mV, 0 mA, 0 mW)
2015-06-22,08:15,KG43,ZR6AIC/KD8QBA,$50SAT,,2990,15689,,,81,3,,21,15,78,4,3536,1573,3339,*7D (3536 mV, 4 mA, 14 mW)
2015-06-22,08:20,KG43,ZR6AIC/KD8QBA,$50SAT,,2990,15689,,,84,3,,22,17,78,3,3556,1573,3339,*78 (3556 mV, 3 mA, 11 mW)
2015-07-07,08:25,KG43,ZR6AIC/KD8QBA,$50SAT,,2990,15706,,,84,3,,22,18,78,1,3475,1590,3319,*7C (3475 mV, 1 mA, 3 mW)
2015-07-09,08:07,KG43,ZR6AIC/KD8QBA,$50SAT,,2990,15708,,,81,3,,22,15,78,3,3516,1592,3319,*7E (3516 mV, 3 mA, 11 mW)

Moreover, when looking at the Battery Voltage/MPPT Current chart, the last set of MPPT (solar) current measurements are well below the trendline, which itself has a negative slope:

https://www.dropbox.com/sh/l3919wtfiywk2gf/AABKSR5V4cOvEPqPYbs8QYZNa/Telemetry-analysis/Current-Telemetry/Battery-Voltage-MPPT-Current-Chart.pdf

Because $50SAT will not transmit if the battery voltage is below 3300 mV, we do not know if it is completely dead or the battery voltage is almost always too low to enable the transmitter.

$50SAT Boards

$50SAT Boards

Our best guess as to what happened is the solar cells have been slowly damaged due to sputtering.  All the high energy particles from the solar wind can effectively “sandblast” the satellite, and since our cells had no protective cover glass, this will cause the surface to slowly become diffused, and thus cause the output of the cells to drop.  We knew this would happen.  What we did not know is $50SAT would operate long enough where this would become a problem; our bets were on the battery failing first.  Since many other CubeSats used the same Spectrolab TASC cells as we did, we are curious about how long it took for the solar output to degrade on these other satellites.  If any of them are reading this post, we would love to hear from you!

We are now in the “how long will it stay in orbit?” phase of the mission.  Thanks to James DeYoung, N8OQ, we have a de-orbit prediction of May of 2017.  From July 6, 2015 to August 28, 2015, the orbital decay rate was about 0.79 km/week.  Earlier this year, it was about 1.2 km/week.  As of August 28, 2015, apogee was at 554 km, and perigee was at 525 km.  We will continue to monitor the TLEs from Celestrak and periodically update the “Orbital-Analysis” folder on the Dropbox.

We would like to extend a very big THANK YOU to the worldwide amateur satellite community!  You helped make our mission a resounding success!  We were able to determine it was possible to make a satellite this small which could generate and store its own power as well as have two-way radio communication capability.  We were able to do this using commercially available parts, including a $10 Li-Ion camera battery, a $10 ISM band radio, and a microcontroller programmed in interpreted BASIC.  We look forward to seeing what the next generation of PocketQubes can do.

73

The $50SAT/MO-76/Eagle-2 team:

Howie DeFelice, AB2S
Stuart Robinson, GW7HPW
Michael Kirkhart, KD8QBA
Professor Robert Twiggs, KE6QMD

$50SAT 19 Months in Space https://amsat-uk.org/2015/06/30/50dollarsat-19-months-in-space/

$50SAT 19 months in Space and still working

Yaesu handheld and $50SAT 1.5U PocketQube

Yaesu handheld and $50SAT 1.5U PocketQube

Michael Kirkhart KD8QBA provides an update on the $50SAT amateur radio spacecraft which measures just 5x5x7.5 cm.

Sunday, June 21, 2015 marked the 19 month anniversary of the launch of $50SAT/MO-76/Eagle-2.  The good news is it still operating.  The bad news is the power situation has been degrading, with an apparent step change on or near May 12, 2015, followed by another on Tuesday, June 23, 2015.  The last full telemetry capture made here in EN82 land was on Wednesday, May 27, 2015, and the last time it was heard was on Friday, June 6, 2015.  I continued to attempt to listen for it for another week or so, and heard nothing.  Has anybody heard it since then?

At this point, I have been monitoring it using Anton’s (ZR6AIC) WebSDR as it makes daytime passes over South Africa.  These occur between 7:30 and 9:00 UTC, which translates to 3:30 and 5:00 AM here in EN82 land.  This is tough, as I am not a morning person.  Sometimes, however, you have to do these things; helping build a satellite might be a once-in-a-lifetime event.  During these passes, where it has already spent a significant amount of time in sunlight, the battery voltage is below 3400 mV.  Is the battery going bad?  While it is certainly possible the battery has suffered from some loss of charge capacity, one has to remember it is does not generate energy; it merely stores it.  Since it is the solar power system that generates the power used by the satellite and stored in the battery, could the drop in battery voltage be due to a degradation in solar power generation?

Back around May 12, I noticed the MPPT (solar) current readings were typically less than 10 mA.  This much lower than it should be.  To better understand what might be going on, a new chart was added to the telemetry spreadsheet which shows both the battery voltage and the MPPT (solar) current (with the zero readings removed), each with its own linear regression line.  This chart can be seen from the following URL:

https://www.dropbox.com/sh/l3919wtfiywk2gf/AABKSR5V4cOvEPqPYbs8QYZNa/Telemetry-analysis/Current-Telemetry/Battery-Voltage-MPPT-Current-Chart.pdf

Notice how the MPPT current trend line has been sloping downward, similar to that of the battery voltage.  Moreover, starting 2 weeks before June 4, 2015 (each X axis division on the chart represents 2 weeks time), each reading has been at or below the trend line.

A more striking comparison can be seen by doing the following:
1. Zoom in of the Battery-Voltage-MPPT-Current-Chart to show the 4 week interval starting May 7, 2015, and ending June 4, 2015
(see https://www.dropbox.com/sh/l3919wtfiywk2gf/AACdQtySHZW3kVl7UMgSrxfHa/Telemetry-analysis/Battery-Voltage-MPPT-Current-Comparison-2015-05/Battery-Voltage-MPPT-Current-2015-05.pdf )
2. Zoom in of the Battery-Voltage-MPPT-Current-Chart to show the 4 week interval starting May 8, 2014, and ending June 5, 2014
(see https://www.dropbox.com/sh/l3919wtfiywk2gf/AACracUWkivilfsKGBUFkmDXa/Telemetry-analysis/Battery-Voltage-MPPT-Current-Comparison-2015-05/Battery-Voltage-MPPT-Current-2014-05.pdf )

$50SAT Boards

$50SAT Boards

In comparing these charts, it is clear both the battery voltage and the MPPT current were significantly lower this year that during the same period last year.  On June 5, 2014, the trend line value for battery voltage was about 3610 mV, and for MPPT current was about 30 mA.  One year later (June 4, 2015), the trend line value for battery voltage was about 3380 mV, and for MMPT current was about 14 mA.  Therefore, while it is likely the battery has suffered some loss of capacity, it appears the low battery voltage is due to low solar power output.  There are many possible reasons for this, including:

* Solar cell damage due to sputtering: since there was no protective covering on the solar cells, impacts from high energy particles can damage the cells, causing a drop in output.

* Solar cell damage due to thermal cycling:  We know from telemetry data the interior of the satellite cycle between +30 degrees C and -30 degrees C each orbit.  It is likely the exterior temperatures experienced higher extremes, and this periodic thermal cycling may have caused the solar cells to fracture, thus leading to a drop in output.

* Short circuit failure of one or more of the diodes which isolate each MPP tracker output, which can cause an inactive MPP tracker (one whose corresponding solar panel is not facing the sun) to load an active one (one whose corresponding solar panel is facing the sun).

Because of the limited amount of telemetry gathered, it may not be possible to determine the exact cause.  If the solar output power continues to drop, the battery voltage may never get above the 3300 mV threshold needed to enable the transmitter, at which point we will lose the ability to monitor its status.  Even if this does happen, however, we never really thought it would last this long.  We would have been happy if it just worked, and really happy if it lasted a month or two.  19 months – this is way beyond what any of us expected!

As of June 25, 2015, the orbit has decayed by about 73 km since launch.  Since April 21, 2015, it has been decaying at a rate of about 1 km per week.  Apogee is now at 561 km, and perigee is at 529 km.

The following are the TLEs from 2015-06-25:

EAGLE 2
1 39436U 13066W   15176.16386703  .00013608  00000-0  90105-3 0  9991
2 39436  97.7444 252.3622 0022818  80.2035 280.1767 15.07230510 86697

Again, if anyone wants to make an attempt at predicting when it will de-orbit, here is some useful information:

Average cross-sectional area = 0.014252 m^2
Mass = 210 g
Area/mass ratio = 0.06787 m^2/kg

From the 2015-06-25 TLEs:
Semi-major axis: 6922.8 km
Eccentricity: 0.0022818
Apogee: 560.6
Perigee: 529.0

As always, please post any telemetry, or for that matter, any reception reports to the Yahoo discussion group.  We would especially like to encourage our friends in the southern hemisphere to listen for $50SAT/MO-76/Eagle-2.  We really appreciate everyone who has provided reception reports and telemetry as well as access to their WebSDRs.  To date, we have 3,098 individual error-free telemetry captures, and the vast majority of these did not come from Stuart, Howie, or I.

73 Michael Kirkhart KD8QBA
$50SAT/MO-76/Eagle-2 team

$50SAT is one of the smallest amateur radio satellites ever launched at 5x5x7.5 cm and weighs only 210 grams. Transmitter power is just 100 mW on 437.505 MHz (+/-9 kHz Doppler shift) FM CW/RTTY. It uses the low cost Hope RFM22B single chip radio and PICaxe 40X2 processor.

$50SAT has been 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.

Further information in the $50SAT Dropbox https://www.dropbox.com/sh/l3919wtfiywk2gf/-HxyXNsIr8

There is a discussion group for $50SAT http://groups.yahoo.com/groups/50dollarsat/

50DollarSat http://www.50dollarsat.info/

$50SAT/MO-76: 15 months, 15 orbits per day, and some unexpected behavior

Yaesu handheld and $50SAT 1.5U PocketQube

Yaesu handheld and $50SAT 1.5U PocketQube

Saturday, February 21, 2015 marked the 15 month anniversary of the launch of $50SAT/MO-76, and you guessed it – it is still operating.

Thursday, February 12, 2015 marked a different milestone – its orbit has decayed to the point where its mean motion crossed the 15 orbits per day threshold.  The TLEs from Saturday, February 21, 2015 indicate it is now at 15.00521293 orbits per day.

Some of you noticed that something odd started happening on Monday, February 23, and Tuesday, February 24.  We also noticed the same thing – during daytime passes in the northern hemisphere, $50SAT was transmitting once per minute, always sending telemetry in RTTY format, but never sending GFSK telemetry packets.  Moreover, the total reset count kept going up by one each time.

Here are all the RTTY telemetry messages (that I am aware of) gathered on Monday and Tuesday:

(daytime pass)
2015-02-23,08:57,KO33,EU1XX,$50SAT,128,,2392,,,56,3,,21,141,77,,2910,1492,3521,*74
2015-02-23,08:58,KO33,EU1XX,$50SAT,128,,2393,,,58,3,,21,139,77,,2910,1492,3440,*72
2015-02-23,08:59,KO33,EU1XX,$50SAT,128,,2394,,,59,3,,21,138,77,,2910,1492,3501,*71
2015-02-23,09:01,KO33,EU1XX,$50SAT,128,,2396,,,62,3,,21,135,77,,2930,1492,3460,*72

(daytime pass)
2015-02-23,17:01,EN82,KD8QBA,$50SAT,128,,2503,,,60,3,,21,137,77,,2910,1492,3440,*78
2015-02-23,17:05,EN82,KD8QBA,$50SAT,128,,2506,,,64,3,,21,133,77,,2890,1492,3400,*70

(daytime pass)
2015-02-23,17:04,EM13,WB2A0Z,$50SAT,128,,2505,,,63,3,,21,134,77,,2779,1492,3380,*74
2015-02-23,17:05,EM13,WB2A0Z,$50SAT,128,,2507,,,65,3,,21,133,77,,2890,1492,3400,*70
2015-02-23,17:06,EM13,WB2A0Z,$50SAT,128,,2507,,,66,3,,21,132,78,,2849,1492,3400,*79
2015-02-23,17:07,EM13,WB2A0Z,$50SAT,128,,2508,,,67,3,,21,130,77,,2970,1492,3380,*7E
2015-02-23,17:08,EM13,WB2A0Z,$50SAT,128,,2509,,,68,3,,21,129,78,,2869,1492,3339,*7C
2015-02-23,17:09,EM13,WB2A0Z,$50SAT,,,2510,,,70,2,,21,,77,37,3677,1492,3359,*70

(nighttime pass)
2015-02-23,18:15,LO24,R4UAB/KD8QBA,$50SAT,128,,2510,,,48,3,,21,146,78,,82,1492,3400,*7D

(nighttime pass)
2015-02-24,03:45,EN82,KD8QBA,$50SAT,128,,2654,,,57,3,,21,138,78,,102,1492,3440,*44

(daytime pass)
2015-02-24,16:57,EN82,KD8QBA,$50SAT,128,,2810,,,57,3,,21,140,77,,2910,1492,3481,*7E
2015-02-24,16:58,EN82,KD8QBA,$50SAT,128,,2811,,,58,3,,21,139,77,,2768,1492,3460,*70
2015-02-24,16:59,EN82,KD8QBA,$50SAT,128,,2812,,,60,3,,21,138,77,,2869,1492,3400,*71
2015-02-24,17:00,EN82,KD8QBA,$50SAT,128,,2813,,,61,3,,21,136,78,,2768,1492,3420,*7C
2015-02-24,17:01,EN82,KD8QBA,$50SAT,128,,2814,,,63,3,,21,135,77,,2849,1492,3380,*74
2015-02-24,17:02,EN82,KD8QBA,$50SAT,128,,2815,,,64,3,,21,134,77,,2829,1492,3380,*75
2015-02-24,17:03,EN82,KD8QBA,$50SAT,128,,2816,,,65,3,,21,132,77,,2809,1492,3359,*77
2015-02-24,17:04,EN82,KD8QBA,$50SAT,128,,2817,,,66,3,,21,131,77,,2910,1492,3400,*74
2015-02-24,17:05,EN82,KD8QBA,$50SAT,128,,2818,,,68,3,,21,130,78,,2829,1492,3339,*7D
2015-02-24,17:06,EN82,KD8QBA,50SAT,128,,2819,,,69,3,,21,129,78,,2849,1492,3339,*73

(daytime pass)
2015-02-24,17:03,EM13,WB2A0Z,$50SAT,128,,2815,,,64,3,,21,134,77,,2829,1492,3380,*75
2015-02-24,17:04,EM13,WB2A0Z,$50SAT,128,,2816,,,65,3,,21,132,77,,2809,1492,3359,*77
2015-02-24,17:05,EM13,WB2A0Z,$50SAT,128,,2817,,,66,3,,21,131,77,,2910,1492,3400,*74
2015-02-24,17:06,EM13,WB2A0Z,$50SAT,128,,2818,,,68,3,,21,130,78,,2829,1492,3339,*7D
2015-02-24,17:07,EM13,WB2A0Z,$50SAT,128,,2819,,,69,3,,21,129,78,,2849,1492,3339,*73
2015-02-24,17:08,EM13,WB2A0Z,$50SAT,,,2820,,,70,2,,21,1,77,35,3698,1492,3359,*4C

(nighttime pass)
2015-02-24,18:16,LO24,R4UAB/KD8QBA,$50SAT,128,,2820,,,48,3,,21,147,78,,82,1492,3400,*72

$50SAT Boards

$50SAT Boards

What seems to be happening on the decending (daytime) passes is the CPU is reset just after sending a full RTTY telemetry message, as here are no GFSK packets sent, but within a half minute the FM Morse beacon is heard with Stuart’s callsign (GW7HPW, the first one in the rotation).  My guess is the battery voltage is decaying during the operational cycle, and goes below the 2.9V reset threshold just after sending the RTTY or just as it is about to send the GFSK packets.  Once the satellite is able to enable solar power (PCB temperature >= 0 degrees C), it starts behaving normally; it is now able to send GFSK packets.  During ascending (nighttime) passes, it behaves normally, at least here in EN82 land.

There was a brief time where this behavior stopped (2015-02-25, 17:05 UTC through 2015-02-26, 3:47 UTC).  It did, however, start back up sometime before 2015-02-26, 05:21 UTC, and has continued since.

Why is this happening now?  We are still investigating, but it is apparent when looking at the chart of battery voltage over the lifetime of $50SAT/MO-76 that the battery has suffered a sizeable drop in capacity.  If the battery voltage under load is dropping below 2.9V, how is it able to recover back above 3.3 V (the minimum required to enable transmission) and nearly complete another operational cycle?  Moreover, why does it always seem to be able to finish sending an entire RTTY packet before resetting?  In the hopes of better understanding what is happening, I am in the process of re-assembling my “BoxSat” test setup in an effort to reproduce on the ground what is happening in space.  In the meantime, the once-per-minute transmission is actually convenient from telemetry monitoring standpoint, as one no longer has to wait 3 minutes for $50SAT/MO-76 to start transmitting.  So, for any of you who have not heard $50SAT/MO-76, now is the time.  Who knows how long it will continue to operate in this manner?  Who knows how long it will continue to operated at all?  Every time an anomaly has occurred and thought, “this is it – well, it was great while it lasted”, $50SAT/MO-76 has proven me wrong.  I hope that is the case here as well.

The Dropbox has been updated with all the telemetry observations through today (Wednesday, March 4 2015), and can be accessed via the following URL:

https://www.dropbox.com/sh/l3919wtfiywk2gf/AABRl4iM5BFqVAcLQGSmdsVga/Telemetry-analysis/Current-Telemetry

I have also uploaded an MP3 file from the daytime pass over EN82 land on Friday, February 27, 2015 starting at 16:59 UTC (11:59 AM local time); it can be accessed via the following URL:

https://www.dropbox.com/s/2vfbtu51qn63aoa/50USDSat-LSB-FM-2015-02-27T1659Z.mp3

During the recording, I switch back and forth between FM and LSB modes so I can hear the FM Morse beacon as well as the RTTY telemetry.

Please keep the telemetry observations coming, especially now!

73 Michael Kirkhart KD8QBA
$50SAT/MO-76 team

$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/

50DollarSat http://www.50dollarsat.info/

Happy Birthday, $50SAT/MO-76!

Yaesu handheld and $50SAT 1.5U PocketQube

Yaesu handheld and $50SAT 1.5U PocketQube

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.
https://www.dropbox.com/sh/l3919wtfiywk2gf/AAC0dF52-SAKbci7gK6iELaja/Telemetry-analysis/2014-11-21

$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
https://www.dropbox.com/sh/l3919wtfiywk2gf/AADn6QqebB-_F7yKXc2RTaU0a/Orbit-analysis

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.
https://www.dropbox.com/sh/l3919wtfiywk2gf/AADw6hSSdaccILYdnpnBTUmta/Arduino-Groundstation

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!

73
Michael Kirkhart KD8QBA
$50SAT/MO-76 team

$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/

50DollarSat http://www.50dollarsat.info/