Most of the popular Inmarsat activity is associated with ships and planes in AOR-E, AOR-W, POR and IOR. There is an Inmarsat satellite called 4F3 parked at 98W that gives CONUS coverage. This satellite is inclined and so does move up and down a bit. This satellite has quite a bit of BGAN services but there is also low rate paging (standard-D) and well as mini-c (standard-C) for fleet tracking. What is fleet tracking? It gives the ability to a company to track and communicate with all of the vehicles that make up a “fleet”. Two way message is possible as well as “polling” (group or individual). The dispatcher can see truck location and provide driving directions as needed.
Example of truck with fleet management.
98W coverage is on left.
On 98W there are currently two mini-c signals, both designated as “private LES” with LES ids of 252 and 253. The protocol is the same as the usual standard-c for the ocean regions but the NCS and LES stations are combined into one. Making some small changes to an existing decoder it was really quite easy to see what fleet tracking is all about. See screenshot below for one bulletin board packet identifying services.
Bulletin Board output.
See the screenshot below for example decode of both private LES simultaneously.
Example fleet tracking decode.
There are many different kinds of trucks that are tracked, some carry petroleum, some carry UPS, FED-EX and AMAZON loads, others more clandestine loads.
Below is a sample antenna that you may see on the top of some trucks that are under fleet management.
The AOR AR2300 is a PC Controlled All-Mode Communications Receiver that spans 40kHz to 3.15GHz. Since the radio is simply a black box with no front panel one must either use the software that comes with it or roll your own. I chose the latter path and wrote my own.
The AOR AR2300 Receiver.
The radio is used with an SDR and so all demodulation occurs in software, therefore only very basic controls are necessary. One feature is a software link to RF Space SprectraVue so that any frequency changes are automatically tracked. Also, the ability to adjust actual frequency for converters that employ a local oscillator.
Too many signals on different bands and tired of manually changing feed lines? Mini-circuits has a nice line of RF Matrix Switches that are USB controlled. I recently acquired a USB-4SPDR-A18 and have now finally gotten around to mounting and installing the new switch.
The switch is made of 4 independent relays that must be wired for proper group operation. The relays are controlled by a small embedded processor with a USB interface.
USB-4SPDT-A18 configured as SP5T (except for one missing jumper).
Since the relays have SMA connectors it is necessary to jumper to some additional SMA to N Female bulkhead adaptors for proper stress relief and cable management.
5 inputs and 1 output.
Bank od sma to N female bulkheads and grounding block.
The final placement, just before wiring. Note the station ground block, this will connect all receivers to station ground system (located near the coax entry area in another room).
Freshly installed microwave switch along with station grounding block.
Here is screenshot of the software that comes with the switch to control the relays.
The sample software from mini-circuits for relay control.
Luckily Mini-Circuits includes a DLL that can be used to customize your own application, which is exactly what i did.
Another new decoder project is in the works. This is another Multi-Channel decoder for Aero but instead of just ACARS and CPDLC it does AMBE and LPC voice decode. The screenshot below shows call logging status output from the prototype decoder. Like the Aero-P project this decoder uses the same control or NCS channels that carries the ACARS/CPDLC traffic except this application focuses on call “following” and directs up to 8 other decoders for actual voice demodulation. Note the captured call highlighted in yellow below. That is a 519 second AMBE call that was classified as non-safety from the aircraft associated with ICAO address 7CF865, which happens to be an Airbus A-300 registered to the Royal Australian Air Force (RAAF). You can look it up yourself at airframes.org.
Status output from decoders.
The AMBE algorithm for Aero is owned by DVSI and therefore requires licensed HW or SW. I am using licensed HW as shown below. This card was available from DVSI but may no longer be due to the inability for them to acquire all the legacy parts to build the boards! I purchased the board a couple years ago for a Mini-M project.
DVSI AMBE DSP Board.
More updates later as the project continues development.This software is intended for commercial use so please don’t ask if you can download it.
Based on the latest Horizons update by JPL (based on Arecibo observations) I have measured the frequency drift of the spacecraft TX frequency (transponder A RHCP). It appears to be drifting upward at a rate of 3.3 Hz per hour. Not bad for such an old spacecraft. This is unlocked carrier frequency measurement over a 3 hour period.
Updated my Horizons data for ISEE-3 today and found this nice note:
Trajectory updated to JPL solution #32 (s32), based on 42 coarse Arecibo plane-of-sky angular measurements spanning May 22 – Jun 23 …
Upon updating things and re-acquiring the signal we have so far a solid signal tracking with little change to frequency. We will see how it performs in next few hours but previously we would observe a 3 Hz per hour change in the frequency. But of course that can just be the unlocked carrier drifting…
I developed this little application a couple years ago to manage shuttle passes for automated s-band reception/recording. I have started using it more for DSN now and so have updated it with some new features.
The tracker gets it’s Ephemeris data via a “Pipe” from other applications, in this case usually another piece of software that interfaces between NASA Horizon database and this application.
The tracker supports Green Heron Engineering controllers via 2 serial ports or an LVB controller via a single serial port.
Besides the usual “Auto Park” and common pointing angles I have added a “Delta” feature to help with off-pointing (validating a signal is coming from spacecraft) as well as spacecraft that are not really where Horizon says they are (ISEE-3) or in special cases like ACE (not in Horizons), where it’s at L1 but offset some number of degrees.
Here is screenshot of the updated application.
pTracker with new features.
Remote operation with this little application allows reception of ACE using the delta controls – without it, i would have needed manual control over the tracking hardware.
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.