How to identify a satellite in orbit
While searching for signals from Russian satellites MKA-N, a signal was detected from an unidentified satellite, which I do not have in the catalog. Let me remind you that the MKA-N devices No. 1 and No. 2 were launched on July 14, 2017 from the Baikonur Cosmodrome and did not contact. For an unofficial reason - because of an accident with the Fregat booster block, although Roscosmos does not recognize this. The manufacturer of these two devices is a private Russian company, Dauria Aerospace. Now Roscosmos demands from a startup 290 million rubles for idle spacecraft ( source ). After 3 days of searching for signals, they were never detected. But another curious signal was discovered. I do not have this device in the catalog, which means it must be identified and entered in its catalog.
First of all, go to the site www.space-track.org and download the TLE of all the objects in Earth’s orbit and load them into the Orbitron program. Orbitron is a satellite tracking system designed for hobbyists and visual observers. It is also used by meteorological professionals and satellite users. The program shows the position of the satellites at any given moment (both in real time and in simulation mode). The program is FREE (Cardware), and is considered one of the easiest to use, and at the same time the most powerful satellite tracking programs, according to thousands of its users from around the world.
We get the coordinates of all the objects in the Earth’s orbit that were in the catalog (16789 objects)
We go into simulation mode and set the date and time when we heard the signal from the satellite. We get a picture of all the objects above the head (for visualization). One of them is our device that we want to identify.
Now, with the help of the calculation, we find out which satellites were overhead in this period of time. Received a figure of 1868 objects. This is to look for a needle in a haystack :-)
It is necessary to reduce the number of devices to a minimum. To do this, you need to know the orbital period of the satellite. We conduct a couple of observations in anticipation of the appearance of the signal and calculate the time between them.
The appearance of the first signal:
The appearance of the second signal:
From the observations obtained, the satellite’s orbital period is approximately 1 hour 35 minutes and 15 seconds (95 minutes). With this period of revolution around the Earth, satellites fly in LEO orbit. LEO orbit (low Earth orbit) - a space orbit around the Earth, having a height above the planet’s surface in the range from 160 km (rotation period about 88 minutes) to 2000 km (period about 127 minutes). According to the information received, we remove satellites from the Orbitron program that fly above this orbit. Plus, you can remove military devices, meteorological devices, GPS devices and communication devices. We get the following picture. Already much better :)
For completeness of observations, we will make another satellite observation with reference to time and get 4 points of the orbit.
Now we have 4 points of orbit when the satellite appears above the horizon:
- March 14, 2018 07:52:10 UTC
- March 20, 2018 07:20:20 UTC
- March 20, 2018 08:55:35 UTC
- March 20, 2018 16:38:50 UTC Using
these timestamps, we create 4 lists with satellites that were in sight. We compare the lists for the presence of identical satellites, and if some satellite is not in one of the list, then we delete it. Do not forget to take into account that the device should not be located high above the horizon.
After all the operations, only one device came up with the parameters: TYVAK-61C.
TYVAK-61C - NORAD: 43144, COSPAR number: 2018-004-AK, Period: 1h 34m 32s (my estimated period is 1 hour 35 minutes and 15 seconds).
Now we determine the exact frequency of the satellite signal. The Doppler Effect will help us with this. The Doppler effect is a change in the frequency and, accordingly, the wavelength of radiation perceived by the observer (receiver), due to the movement of the radiation source and / or the movement of the observer (receiver). The effect is named after the Austrian physicist Christian Doppler.
Now, knowing the parameters of the orbit, we calculate the Doppler effect. With such parameters of the orbit at a frequency of 400,000 MHz, it will be ± 0.009520 MHz.
Knowing the frequency when the first satellite signal arrives, we calculate the working one, compensating for the Doppler effect. It turns out - 401.050 MHz.
We check the calculations in real time. We are waiting for the next passage of the satellite and see how the signal will diverge from the calculated one. If there are big differences during reception, then this is not the device, if everything is accurate, then this is the TYVAK-61C satellite. We launch the receiving station. We got a discrepancy between the frequency of reception and the frequency of the satellite signal (the signal from the satellite appeared at a frequency of 401.042 MHz, and the calculated frequency of reception should be 401.052 MHz).
The discrepancy can be for two reasons, the first - the satellite was not correctly determined, and the second - the time and frequency scale on the previous screenshots (frequency overview scan) has a small error. 95% is to blame for the second reason. Knowing the position of the satellite in space, the exact time of signal reception and the frequency of signal reception, we recalculate the Doppler effect. We get the frequency 401.040 MHz. We set the receiver frequency to 401.040 MHz and monitor the signal frequency and the calculated frequency.
Now, the frequency of reception, taking into account the Doppler effect, is converging. And we can safely say that this is the TYVAK-61C satellite.
TYVAK-61C is an American astronomical satellite manufactured by Tyvak Nano-Satellite Systems, Inc. The device is designed to catalog changes in the light of stars. The satellite has dimensions of 10 × 30 cm (3U CubeSat). TYVAK-61C was launched on January 12, 2018 from the Shrikharikot launch site in India. Unfortunately, I did not find the image of the device on the Internet, but approximately it looks like a NanoACE satellite.
We switch the receiver from a surveillance antenna to a directional one with a rotary device. We will try to receive information from it and decode the signal.
We identified the satellite, determined the frequency of the signal and decoded the signal :-) Call sign of the satellite: GEOSF1.
→ The device is listed in the frequency table
→ The device is added to the satellite list
→ How to add the SATONLINE base to Orbitron