We live in interesting times. In orbit is the Polish student satellite PW-SAT2 which broadcasts data in our radio-amateur band of 70cm. The history of the PW-SAT2 project is also described in Wikipedia and on the website of the Student Astronautical Circle. There is also an interesting photo gallery from the implementation of the PW-SAT2 project. Data broadcast from the satellite can be received and legally decoded, which is encouraged by the announced competition for radio amateurs.
Today I encourage you to take advantage of the opportunity to receive data from the Polish satellite. Even one received package can contribute to the collection of a full set of data.
On 29. 12. 2018, at 9:12 am local time in Poland, the first attempt to open the sail was planned, that is, to perform the main task of the mission of this “artificial bird”. After opening the sail, the satellite will stay in orbit for about a year, but a large sail will cause solar panels to cover and a power shortage. It is estimated that in about three days the satellite may be silent, so this is the last chance to hear it.
If the PW-SAT2 team fails to establish communication with the satellite in the first term, then another attempt will be made on the next flight at 10:47, on the same day. If the second attempt fails, the next tests will take place only on January 5, 2019 (at 9:52 and 11:27) – as PW-SAT2 team informs.
Based on conversations with colleagues, I learned that the satellite signal is visible on the SDR even for external omnidirectional antennas. By default, the satellite works with a transmission of 9600 baud, however, just as during the sail opening operation, slower data transmission of 1200 baud will be enabled. The transmission speed translates into the emission width, and for slow transmission the PW-SAT2 signal width is narrower than the standard width received by our radio communication devices. At 9600 baud, the signal is so wide that you need to use SDR, because not all radios will be able to pick it up. In other words, the signal should be heard, but it can not be read.
The position can be read from the PW-SAT2 website (https://radio.pw-sat.pl/), or from the program, eg Polish by Orbitron. TLE data from which you can count the satellite flight within radio range of the station can be found in the file new-background.txt under the name PW-SAT2.
You must install Run_PW-Sat2_Ground_Station for decoding data. In order for the program to transmit data to the server, one must create an account at https://radio.pw-sat.pl/signUp, and after confirming the e-mail address (clicking the link in the received e-mail), “credentials” are downloaded, which are loaded to the Run_PW-Sat2_Ground_Station program. The simplest configuration is as follows: antenna (or LNA) => SDR => program “Run_PW-Sat2_Ground_Station”.
It is necessary to correct the Doppler shift by alnbop manually (approx. +/- 10kHz), or automatically eg by the GPredict program, description here: https://github.com/PW-Sat2/HAMRadio/wiki/Doppler-shift-compensation. Program here: https://sourceforge.net/projects/gpredict/files/Gpredict/2.2.1/
Thank you Piotr SP5ULN for valuable information on how to decode PW-SAT2.
More about the data collection you can find, among others on the SP7PKI online forum: http://sp7pki.iq24.pl/default.asp?grupa=101438&temat=349738&nr_str=12
And in Polish: https://pw-sat.pl/informacje-dla-radioamatorow/ or in English: https://github.com/PW-Sat2/HAMRadio/wiki
Info: Armand SP3QFE
Number of Comments: 8
It is a pity that I did not get interested earlier. Theoretically, I could pick up some 1200 baud frames using FT991 (USB, 3.2 kHz bandwidth) and my omni-directional antenna.
Today I installed the software as described and I can risk that it works. I am ready to receive the “last chance” on Saturday, January 5 at 9:52 and 11:27.
Today, around 10pm, the satellite flew over Germany, and by turning the knob (Doppler correction) I heard a few regular signals with the character of an increase in noise. The detector did not detect any frames. Or maybe it seemed to me? hi
Mirek SP5GNI
Hey!
PW-Sat2, the second student satellite was launched on December 3, 2018. We was able to get the contact with it immediately, and thanks to the software prepared by the tean (and companies cooperating with it), all planned experiments and their results were sent by radio very fast! The team said before Christmas that most of the experiments (including taking photos) went well. This is also due to amateur radio players, who have been very active in the action of collecting telemetry data sent by our satellite.
At this point, the satellite is already in the end of its life, because recently opened a deorbiting sail – one of the last exesperants. This sail is intended to slow down the satellite in a residual atmosphere that occurs on a low LEO orbit and accelerate its combustion in the Earth’s atmosphere.
Personally, in home QTH I have a problem with the reception, due to the large interference occurring in the band of 70cm. Vertical antenna and FT817 or BladeRF do not give me a chance to receive in my area, but I do not give up my attempts and as soon as there is a flight I am near the radio, and I set my radio for 435.275MHz.
At this point, PWSAT2 mainly broadcasts with a fast bitrate, and the team willingly shares all information about the life of the satellite on its Twitter
Kamil SQ5JRN
Why PW-Sat2 sail is not equipped with photovoltaic cells? His predecessor – PW-Sat – was to have a folded tail covered with the cells.
SP5JSZ
Zbyszek
PW-Sat 1 did not have a tail covered with photovoltaic cells. It was a structure, like in PW-Sat2 made of very thin foil, which gave the possibility of folding it to a small size, to which photovoltaic cells would not allow. The deorbiting sail in PW-Sat2 was very tightly rolled up, which during the work was a huge mechanical challenge – the silicon structure of photovoltaic cells would not allow it.
As for the photovoltaic cells themselves in the context of power supply – they are used. There are even bigger (in surface) than in our first satellite. PW-Sat1 was 1U (10x10x10cm) and had cells on 3 sides. PW-Sat2 is 2U (20x10x10cm) and has two long sides and half of the third one, 20x10cm more.
Kamil SQ5JRN
Kamil
explain it please. Because at https://pw-sat.pl/pw-sat/ there is info:
“The PW-Sata deorbitation system consisted of a structure called the tail. It had the shape of a spring with a square shape and a length of about one meter. The sides of the tail were covered with flexible photovoltaic cells attached to the spring. ”
In turn on https://pl.wikipedia.org/wiki/PW-Sat2 there is (about Sat1):
“The idea of using the sail as a deorbiting system appeared among students of the Warsaw Technical University in 2004 during the design of the PW-Sat satellite. At that time, it was finally decided to use a folding tail covered with flexible photovoltaic cells. ”
I understand correctly that these descriptions relate to the original intentions, and ultimately Sat1 has been equipped with a tail without cells?
SP5JSZ
Zbyszek
you’re right, I misinformed that it was just a foil structure. Because of the fact that they were supposed to be flexible cells, it was a form of a tail, which thanks to its construction could be folded. The tail then had to perform two functions, an additional power supply and drift-anchor.
In PW-Sat2, the focus was only on the braking function, so the most important was the size. A 2m x 2m sail could not be folded if it was not made of such a thin and flexible material. The flexible cells used in the tail would not give this possibility.
I am sorry, for misleading
Kamil SQ5JRN
Kamil, thanks.
This is one more thing. Was the PW-SAT2 orientation control system unable to position the satellite in such a position that the sail would not cover the cells after opening? That it would be conventionally “downstairs”, in other words between the satellite and the Earth, not the satellite and the Sun? For the deorbiting itself, the position of the sail is probably not significant?
Zbyszek SP5JSZ
Zbyszek
orientation control system (ADCS system) in PW-Sat2 consists of two coils, which, powered by electricity, are to create a magnetic field around them. Theoretically speaking, this field would set up the satellite in accordance with the Earth’s magnetic field.
However, the presence of the system and its operation in PW-Sat was mainly aimed at decelerating the satellite’s rotational movement after its ejection from the rocket and from the tray in which the satellite was being carried by a rocket. This behavior of the object at the very beginning well illustrates the animation: https://vimeo.com/57528833
With very low resistances, such a move could last almost infinitively, and this could lead to communication problems, or the opening of the sail could easily be damaged.
As for the sail issue, he should rather be perpendicular to the plane of the earth, and thus should not cover the sun – in the end, the satellite still circles the ground, not falling like an object with a parachute. So, theoretically, there should be no problem with covering the panels with a sail. The fact that in some photos it looks like the satellite is positioned differently is caused by free rotation in the almost-vacuum. On the satellite finally the forces that acted from the law of conservation of the momentum when opening the sail, which was mounted on two types of springs, acted.
Coming back to ADCS – this system, eats up the current dispute, and drawing lessons from the PW-Sat1 experience, this aspect was very much guarded. The ADCS had, as I wrote above, mainly slow down the rotation of the satellite when it was in orbit, and then act only at times when the rotational speed would rise to the set limit values.
Zbyszko, did I answer your questions?
Kamil SQ5JRN