Atlas V 401 - Landsant 9 - 2021-09-27 18:12 UTC

Thanks for the update, Emil.

Many stations are capable of receiving 400.5 MHz & also decoding 38k4. Will CuPID only downlink immediately when receiving a command from the ground? Or, once a command is received, will there be transmissions from the satellite for some (???) period of time after?

Also, from what location(s) will ground commands be sent. It would be helpful to know when the satellite might be heard.



Hi @K4KDR - Thanks for your help. CuPID is working from a ground station at Boston University.

The design of CuPIDs ground pass begins with 3 commands from the ground that tell the satellite to open some filters, and stream an EPS packet. From there we command it to stream more data packets. After looking at live data packets, we then try and downlink a file. CuPID will not downlink files unless it receives a specific command from the ground.


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Very good - thanks! So depending on the satellite’s transmitter effectiveness, I might have a chance to receive it here in Virginia. Ditto SatNogs stations in the region.

I’ll try to watch for it as often as possible but if you would like to post somewhere when you intend to attempt uplinks, that might increase the number of stations listening on the ground.

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Hi @ematz and welcome!

Thank you for the details about CuPID.

About the TLE sets, CuPID’s orbit is described from one of the following (source

1 49261U 21088B   21271.93862092  .00004000  00000-0  32217-3 0  9995
2 49261  97.6253 339.9480 0022102 249.0096 110.8769 15.00318609   161
1 49262U 21088C   21271.93862092 -.00008855  00000-0 -69621-3 0  9999
2 49262  97.6215 339.9481 0021940 248.2474 112.3009 15.00476349   161
1 49263U 21088D   21271.93774192 -.00005522  00000-0 -42110-3 0  9995
2 49263  97.6240 339.9472 0017328 244.9374 115.0011 15.01538841   167
1 49264U 21088E   21271.87104219 -.00010846  00000-0 -83052-3 0  9991
2 49264  97.6227 339.8824 0016098 252.5125 107.4340 15.01631683   152

Currently all of them are close enough, so for reception any of them should work for now. Also our findings is that 49263 is CUTE, so the other three are good candidates. Depending on the angle of your transmission beam, trying all these TLE sets interchangeably would be a good strategy.

As @K4KDR said, knowing the timestamp of your transmissions and the TLE that you follow will be very helpful for us to organize the observations of our stations and have better chance to receive it.

Tracking CUTE as 49263 last night worked extremely well; our best downlink to date. We also just completed our pass with commanding and it also worked exceptionally well. We saw beacons from 0º elevation rising to 0º elevation setting and were getting commands in at <5º elevation on both sides.


Ditto on letting us know about uplink times, I prioritize my station #2134 time to satellites flown by educational institutions. … and I’m in western MA :slight_smile: So lots of overlap.



CUTE is now identified as OBJECT D(49263), here are the results of ikhnos on observation 4792784. NORAD ID is now changed in DB and Network, if someone uploads data on the temporary NORAD ID will be merged with the satellite in the next days.


What is the best way for us to let you know when we operate the ground station? Observation SatNOGS Network - Observation 4800843 looks like our ground station. Thank you for listening!!!

I can clearly see our commands in there coming from Boston, but then I am unsure of the signal between ~130seconds to 190seconds. Maybe thats CuPID?

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I have another pass coming up in 35minutes and the antenna will be pointing at 12 degrees over western MA @satcolintel5

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@ematz I’ll check the observation to find out if the signal is from CuPID.

About the best way to let us know, a UTC timestamp as soon as possible it will work fine.

For the pass in the next 35min we have already scheduled CuPID, let’s see!

Just to be clear, are you 100% sure that the signal at ~50s, ~100s, ~230s, ~350s and ~400s comes from your station? This signal fits good the TLE sets from OBJECT B and C, so I guess you follow one of them for doppler correction, right?

Unfortunately for the signal starting at ~130s is difficult to say if it is CuPID, mostly because of the bandwidth of the signal, which doesn’t look right for 38k4 bitrate except if I got something wrong. I guess we would expect something like the other signals in the waterfall as a response. Also the duration is so short to tell if it is terrestrial or if it comes from space.

Some questions that may help to spot a reply from CuPID:

  1. How fast CuPID is going to reply to a command from the ground station? For example in this waterfall, if the signal is from CuPID it seems to take ~30s to respond, could this be valid?
  2. How long the transmission from CuPID will last? Is there a specific duration? Again if the signal comes from CuPID it looks like a 60s transmission.

Quick update regarding the pass in 10 minutes - Ground station will not be emitting because the ISS is overhead and our FCC license doesn’t allow us to transmit when the ISS is in view.

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Signals at 50, 100, 230 350 and 400 look like me commanding. We have two common commanding methods:

  1. Most commonly, we send a sequence of 3 commands 0.5 seconds apart to 1-block all telemetry, 2- filter telemetry to just EPS data, 3- stream telemetry. Indefinitely until a later command tells it to stop.
  2. Another command we do, we send 1 command and CuPID internally does the same commands like before but with more than just EPS data and it only lasts 15 seconds.

During that last pass, 4800843, we started with object E and then tried tracking object B which was right behind it. It looks like these are from when we were tracking B.

I agree, the signal looks a bit strange and looks a bit like an outlier in the command sequence.

  1. CuPID’s internal heartbeat is 5 seconds. If command enters just after a heartbeat, it will be 4-5 seconds before a response. If a command enters just before a heartbeat, it could be 1-instantaneous before response.
  2. That depends, if it gets command sequence 1 or 2 described above. 1 is indefinite until it gets stopped. 2 is only 15 seconds with more data.

Update on the current ground pass - ISS left view half way through. I threw out some command towards western MA.


Here’s a result from that last CuPID pass about 30 minutes ago from my station in Western MA

CuPID was skirting along the limits of my elevation mask to the west (mountain 9 - 12 degrees) so even if there was signal, it would have been a hard to acquire. I’ve left the observation unvetted in case you can spot something in the waterfall that escaped my eyes.


Thanks for sharing. I was just looking at that. I don’t see much there. If your antenna was also pointed at CuPID then that makes sense why we don’t see my commands. Is there a time we can schedule so you can point at Boston and I point at you to see if our antenna is emitting appropriately?


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Absolutely, glad to help. The location of my station here is fairly accurate (within a mile or two). The highest point on the Mass Pike is to my east ~1700 ft @ ~ 20 miles so not sure I’ll be able to pick anything up from Boston. Willing to try though :slight_smile: Let me know some times you are available. I emailed Brian W. @ BU directly a few days ago, he has my email address if that makes this easier for comms.