Isro SSLV-D3 - 2024-08-16 03:47 UTC

[fredy]

@K4KDR thanks for your analysis! It is very useful!

Correct me if I’m wrong, I have the impression we have seen in the past LoRa signals received and decoded when the satellite wasn’t in the station field of view. From your screenshot it looks like it was pretty close to the station, so it may be one of these cases.

Anyway we’ll keep tracking SR-0 the next days, just to confirm the identification and also just in case we need to generate a TLE set if space-track doesn’t update regularly their own.

[K4KDR]

Good point - ‘out-of-position’ LoRa decodes on tinyGS have been, and in many cases continue to be, because many the identity of the transmitters being tracked are “best guess” situations. A good number of the satellites in orbit transmitting via LoRa are not publicly documented, so the community has had to try to match RX reports over time to what the source of the observed signals might be.

Naturally, first attempts are often incorrect. Combine that with the high likelihood that a portion of these signals are coming from ‘constellations’ of multiple commercial sats and now you’re seeing decodes attributed to the one best-guess object when in reality, identical downlink signals could possibly be coming from multiple satellites - making the orbital matches look ridiculous.

[K4KDR]

Very pleased to help conduct the first UPLINK testing to SR-0!

After settling on a little 8-watt RF amp ( https://www.aliexpress.us/item/2251832661066378.html ) to boost my TX signal (via the 70cm Wimo X-Quad RHCP) -and- running my AZ/EL tracking computer ahead 3.5 minutes last night to “cheat” on the TLE, multiple uplink commands were received by the satellite, including a command requesting the downlink of a message body provided to me by the SR-0 Team that I had uploaded to Mailbox Slot-1. (99 Mailbox slots are available)

Here is the tweet from the Team ( x.com ) announcing success after it was received by over -50- tinyGS stations along the U.S. East Coast last night…

… perhaps even more cool is that hours later, we’ve seen confirmation that a SCHEDULED message downlink that I queued in one of SR-0’s -3- ‘Scheduler Memories’ was apparently received last night, resulting in a Mailbox Message downlink at a specific time today over India!!

(you can see by that screen capture that because of the position of the satellite being several minutes ahead of where the TLE expects it, the downlink TIME calculation that I used in the scheduler came very close to missing the tinyGS Ground Stations in India!)

I’m sure the SR-0 Team is working as fast as possible to make their Ground Station UI available to everyone – for the moment, my testing is w/ various fixes & hard-coded items - as is often the case in the early days of application development. I’ll certainly look forward in the near future to seeing traffic to/from SR-0 from anyone w/ a LoRa device & licensed to TX on 437.400 in their home country!

I should add that we also have the ability to uplink command instructions to downlink using FSK instead of LoRa + the option to TX via the 1-watt radio (instead of the default 100mW transmitter). I’ll certainly try that as we work through trying to test the various capabilities of SR-0!

[tomasz]

Great Job !

How much power did you achieve using this amplifier?
Did you connect it directly to TTGO or some other device?
Is there a set of commands that you can share and that can be tried ?
Are we waiting for the official GUI station application for now ?

[K4KDR]

Many thanks!

Don’t know about actual TX power, but I’ve ordered a long over-due 525 MHz watt meter, so I should have more info on that next week.

I guess this is true of any RF amp, but the documentation does mention that output is proportional to input power (as well as DC electrical power) to the amp. So, to squeak out just a LITTLE more power, I’m using a Nucleo STM32WL55JC2 for this at the 22 dbm TX level. Just about everything else I have has a max TX power on paper of 20 dbm.

I’m sure that the SR-0 Team is as anxious as I am for more stations to be uplink capable. In fact, several to-do items on their Ground Station UI were finished today - it was great to see many of the known checklist items be completed.

So, after a VERY few more to-do’s, I’m guessing that they will post the details.

In summary, there will be multiple ways to uplink commands to SR-0, depending on the hardware available and the operator’s comfort level. The basic & I’m sure most commonly used commands will be:

==store a message in a particular mailbox slot #

==request downlink of the message from a particular mailbox slot # (specifying that the downlink be either LoRa or FSK and either using the 100 mW radio or the 1-watt radio)

In no particular order, an operator could:

#1: manually create commands following the uplink command syntax (a few comma-separated fields) ended w/ a ‘|’ character + a checksum (easily available via a web calculator URL) & transmit the combined payload through the tinyGS web GUI or any interface that they might have on-hand to transmit a given array of hex bytes out their LoRa device

#2: use the SR-0 Team’s Ground Station UI to assemble the command + checksum and copy/paste the resulting hex for TX via any of the same methods mentioned above

#3: run a fairly standard RadioLib-based Arduino sketch (provided by the SR-0 Team) to interface to your LoRa device & then connect via serial directly from the SR-0 Team’s Ground Station UI… then you can transmit (or receive) directly within the UI. That is what I’m doing. Glad to help anyone who needs a hand running that Arduino sketch on their particular microcontroller… I’ve connected to a good percentage of the most commonly used LoRa-capable microcontrollers so I already have the settings.

… about the only other thing to stress is that while the Team’s Ground Station UI is absolutely setup for both RX & TX, if you’re using a cheap solid-state RF amp like I am, you are a TX-only station and will depend on the kind contributions of the decodes received by others to know what’s being downlinked. I have the good fortune of having a remote connection to super-station N6RFM which receives everything that SR-0 even THINKS about transmitting, so that’s very helpful. I suppose one day I should man-up and build a relay scheme to bypass this amp when not transmitting. But I need to walk before I run. Hope that’s helpful!

A final note considering your location… if I have any luck with tonight’s tests, you may wish to monitor SR-0’s downlink around August 25, 2024 23:25:15 UTC… no guarantees but one of my to-do’s for tonight’s U.S. passes is to try to schedule a mailbox message downlink (via LoRa) at that time when the footprint is over a portion of that region.

[K4KDR]

Regarding the TLE from Celestrak for SR-0 (currently showing as object 2024-147B), as of the 0300utc pass on 25-Aug, decodes observed on tinyGS stations now DO match the TLE. So, that’s good news for sure!

[K4KDR]

Well, I don’t know (yet) if my attempt to place an ‘EU’ message in SR-0’s Mailbox-3 was successful or not… nor do I know if my attempt to schedule a downlink when it’s at max elevation over that region some hours from now was successful, but I sure did try.

However, I was able to downlink a new message that I uploaded to Mailbox-2, so the testing is moving in a positive direction! (… and thanks to several dozen tinyGS stations for catching the downlink since I was in TX-mode)

[dl7ndr]

Well done, Scott.

Since SR-0 gets only 14° over horizon at my location, 1 watt instead of 0.1 could make me decode it finally.

[K4KDR]

Question from last night has been answered!

SR-0 obviously DID receive both my upload of a new mailbox message and later a command to schedule the sat to downlink this message at a time of highest elevation over Europe. As you can see on the map (one of FOUR separate posts of this single downlink on tinyGS - I can only guess that it breaks up the logging of a decode by SO many Ground Stations at the same time), stations from all over the region decoded a message from the SR-0 Project Team!

[dl7ndr]

Confirming!

Last night I finally received SR-0’s LoRa beacons pointing my antenna fix to 180° and 8° (should be exactly looking at the satellite’s position on you screenshot).

And here it is:

23:25:26 9:0:id:12 cr:7 len:74 crc:ok lev:-13.7(-18.2/-10.1)dB snr:-2.6dB nf:-38.2(-39.6/-37.1)dB txd:69 t:565 q:96% fc:47 afc:1752Hz dre:8.7ppm
[++++++++++++++++++]SR0SAT[10]u[02][01][03]=Hello Europe from Chennai India - the home of satellite SR-0!Z

Looking closer it reveals this beacon as message type 2 ([02]) transmitted at 1 watt ([01]).

Umong the other 12 beacons I received with crc:ok, there was one beacon with message type 3 ([03]) right after the message beacon above.

23:25:26 9:0:id:12 cr:7 len:17 crc:ok lev:-22.0(-23.9/-20.5)dB snr:-9.7dB nf:-39.6(-40.0/-39.1)dB txd:65 t:188 q:95% afc:1174Hz dre:13.7ppm
[+++++]SR0SAT[11]u[03][00][95][FF][01][00][00][00]{

Scott or maybe @riftron do you have an overview of the message types to be able to update the SatNOGS SR-0 decoder to process all types correctly to show them on the dashboard?

[K4KDR]

I’m sure the Team will include this in the documentation when they release everything, but I can’t imagine they would mind if I provide it here to give you a head start. (However, please confirm these values when final documentation comes out - you know how things can change on these projects!)

SR-0 DemoSAT
Message/Packet Types
---------------------
1 Satellite info
2 Store And Forward Message
3 Uplink command response
7 IMU Data
10 HMS Power Data         (health monitoring system)
12 HMS temperature data   (health monitoring system)
13 Radiation data
14 System Config

[dl7ndr]

FYI:
Yesterday evening I received an (crc:err) S&F message from SR-0 and the following packet with type “Uplink command response” at 21:37:16 produced a peak at the dashboard’s graphs.

[K4KDR]

Yes, that was a real mystery. There was a scheduled downlink that triggered at that time:

… but no one in that footprint would have been transmitting commands. So, it’s very difficult to say what caused that Command Response ‘ACK’ type of downlink. There have been many other scheduled downlinks and I’ve not seen that behavior when they triggered.

[PY4ZBZ]

[dl7ndr]

Nice tool, Roland!

Does it also show messages other than type 1?

[PY4ZBZ]

TNX ! No, Is there another mode? Description? 73 !

[dl7ndr]

There are more modes, but we don’t have more information yet than the overview from Scott.

[K4KDR]

And while I don’t have the full break-down of all the downlink types, watching the decode of the Type-2 “Store-and-Forward Message” downlinks on tinyGS, it appears that the 11th byte is the Mailbox Number (1 thru 99 in HEX). So that’s very handy!