It’s been an S-Band weekend here. Earlier today the Indian Spacecraft MOM was picked up by DF2MZ as well as UHF-Satcom at a distance of 107 Million km! By the time the spacecraft rose over California Goldstone had locked it up to their ground station and data was being transferred. The signal was well down into the noise, but using some amount of integration the signal was detectable (as shown below). After a few hours Goldstone stopped the data transfer and unlocked the signal, the signal immediately increased in strength and moved to the calculated Doppler target, where it remained for the evening. You see Doppler in the locked signal because the spacecraft is compensating for the Doppler (locking to the ground signal), where on the unlocked signal you don’t see any Doppler, this is because it is being compensated with software using NASA Horizon data. The exact unlocked frequency was 2292.960847 MHz.
MOM going from locked to unlocked.
Here is a nice website that gives you the real time status of the DSN (click on image to go to the site).
ISEE-3 (ICE) Spacecraft was detected today using a 1.2m dish at 2270.390831 MHz. The signal at this frequency was also simultaneously detected and confirmed by Paul over at UHF-Satcom. The detection was accomplished by integrating multiple FFTs with the spacecraft TX frequency corrected for Doppler. Without precise Doppler correction the signal would not be detectable – I confirmed by turning integration off. I also confirm target by off-pointing the dish confirming loss of signal in multiple directions. The Doppler correction is accomplished with an application that takes NASA Horizon data and calculates a real time adjustment to the TX frequency of the spacecraft. This adjusted “offset” is then used to update the SDR IF frequency. The software that makes this possible was written by r00t in .cz.
Below is a screenshot that pretty much sums things up.
The Lunar Reconnaissance Orbiter (LRO) is a nice S-Band (2271 MHz) signal coming from the moon to calibrate your dish. This is especially helpful if you need the accuracy for even higher frequencies where the beam-width is narrower. Below is a screenshot after optimization of LNA assembly, calibration of azimuth and elevation as well as adjustment of phase center of the feed.
LRO wilth doppler and sidebands.
The LNA assembly and feed shown below is just temporary for this measurement. Normally the LNA is located a few meters away inside an equipment box but for this peaking i wanted to remove all feed line loss.
Inmarsat Aero-P includes an ACARS service for airlines to use while transiting the various ocean regions. This is much more reliable than HF ACARS. Inmarsat hosts 3-4 Aero-P control channels on L-Band for each ocean region. Each control channel is running OQPSK at 10.5K bits/s rate. This new decoder is actually 4 decoders in parallel and is capable of monitoring an entire ocean region. Currently both RFSpace SDR-IP and NetSDR is supported as well as the QSDR. The required bandwidth is 200 KHz. I can make this work with 190 KHz which would then add the SDR-IQ (with Ethernet server app) to the list of supported SDRs. As usual, this decoder interfaces over Ethernet. Below are a few screenshots of the working prototype.
Here is plot of the 4 channels from the IOR region. These are always on and continuous transmitting so they are easy to find.
IOR Aero-P Control Channels.
The next screenshot is POR region. You can see the 3 Aero-P channels in the IQ Viewer in lower left. Above that are logging windows for each channel, in POR case, there are 3 channels. The other console window is the main decoder log, shows current SDR status, Signal Unit count, ACARS traffic count, CPDLC counts as well as log-on events. All traffic is sorted per aircraft and written to disk – so everything is archived.
POR Aero-P ACARS Sample.
Here is a sample from UHF-Satcom for the AOR region (thanks Paul).
AOR region Aero-P ACARS sample.
Here is a sample from another user monitoring IOR region.
IOR region Aero-P ACARS sample.
There is support for streaming all TEXT ACARS messages over to Plane Plotter.
Aero-P ACARS on Plan Plotter.
Below is screenshot of directory where messages are stored. You can see in this case there is some trouble with WIFI.
Support for ACARS Display was added, which is a step up from Plane Plotter IMO. You can see that ACARS Display will automatically look up the ICAO based on registration number.
ACARS Display Support.
If you click on one of the registration numbers (such as B-HKU) you will be brought to a website that will give you up to date information about that aircraft (as shown below).
Below is graphical overview of Marine-C, an Ethernet based Multi-Channel Inmarsat-B decoder. The decoder is able to simultaneous decode up to 12 channels and therefore can cover an entire ocean region with this single application. The decoder monitors all LES channels as well as the main NCS channel and properly decodes all messages and bulletins, including data and text. All results are automatically saved and can be left un-attended without missing anything. Two SDRs are required because the NCS and LES channels are too far apart to capture with single SDR.
Overview of 12 channel Standard-C Decoder.
Below shows some sample output for message status, LCN and SDR status. Also shown is FFT of NCS and various LES channels. You don’t need to run the IQ viewers for normal operation.
FFT of NCS and LES along with message and LCN status.
The output is directories with text and data files as shown below.
File output examples.
Since this application is entirely Ethernet based you may be wondering how I am using the SDR-IQ, which is USB based.
The SDR-IQ is hosted on a Raspberry PI and serves up the appropriate Ethernet packets so that the main decoder application just sees another SDR-IP or NetSDR.
Persistence and coffee helped to produce the two images below of the Lunar Eclipse last night. I was fighting high wispy clouds all night. The 1st magnitude star Spica was conveniently parked next to the moon and made for a nice photo op.
Spent some time with the big gas planets and Mars. Mars is closest to Earth since 2007 and is still pretty hard to see. Jupiter turned out nice. Saturn was a bit out of focus, seeing was not too good. Will try again in May for better Saturn image.
Here is a shot of the telescope. This is remotely operated, not local.
Below is a graphical overview of Marine-B, an Ethernet based Multi-Channel Inmarsat-B decoder.
Overview of Multi-Channel Inmarsat-B Decoder
Below is a more detailed block diagram of multi-channel decoder with a few screenshots of operational logging and FFT waveforms.
Marine-B is a fully automatic frequency agile Inmarsat-B multi-channel decoder. The decoder supports BPSK for NCS call logging/directing, OQPSK for APC voice demodulation, real time audio output and automated MP3 audio file archiving. It can handle as many voice decoders as CPU capability allows. Initial testing with multi-core i7 Intel CPU comfortable supports 6-12 parallel channels.
The decoder only supports RFSpace SDR-IP or NetSDR SDRs.
Here a a couple of short sample voice decodes (these are generic and do not violate any privacy).
This is a multi-channel Inmarsat B Decoder. It uses a single RF-Space SDR-IP to receive L-Band IQ data via Ethernet and then does all demodulation and decoding in software. The demo below has 5 voice decoders, although only 2 are active during the demo. More channels are possible depending on CPU capabilities. In addition to the voice channel decoders there is a NCS control channel decoder that is responsible for all channel assignments and coordination. Although voice is shown in the demo, both data and fax are also possible.