PW-Sat2 satellite deorbit sail will be deployed sooner than we have initially planned. The original schedule of the mission assumed that the satellite’s deorbit system will be activated no later than on the 40th day in orbit. However, several factors have affected the decision to bring forward its deployment. The first attempt to send a signal to open the sail will occur on the morning of December 29th.
How will the operation proceed?
The deployment of the sail will occur on signal and will be monitored by our ground stations. The course of the experiment will be recorded by a number of sensors and the onboard camera will take a picture of the opened sail. The unfolding of the deorbit sail is a very dynamic process, which will probably result in the satellite spinning without control. This will significantly hinder receiving data (including pictures) from the device. For this reason, we encourage radio amateurs to listen for the data with us. Thanks to them, we are hoping to receive more data than it would be possible using our two ground stations in Warsaw and Gliwice.
We are planning to send the telecommand to the satellite during our morning communication session. However, previous experience suggests that a stable connection necessary to conduct the whole procedure will be acquired during one of the following sessions on that day, around 10:50 a.m. local time.
Why are we deploying the sail sooner?
The main reason for the rescheduling of the sail’s deployment is the desire to lower the risk of mission failure. During four weeks of work since December 3, 2018 we have managed to complete all planned tasks, greatly exceed expectations and successfully conduct about 150 communication sessions with the satellite.
Our satellite was already threatened by space junk
Not without significance is also the fact that we have received a warning from an American bureau dealing with the tracking of space debris (CSpOC) about an object posing a threat to PW-Sat2 satellite. During the last couple of days, we have monitored the estimated distance at which the object designated SCC #39841 was supposed to pass our satellite at the speed of about 3.6 km/s on December 27th at 9:03 GMT. The distance was initially estimated to be 147 metres, then 95m and finally around 79m. These kinds of situations happen relatively often in orbit, but we didn’t expect the first warning we would get to concern such a small distance.
This event brilliantly illustrates why PW-Sat2’s mission is so important and the problem of space junk so relevant. During just 20 days in orbit, PW-Sat2, which is only a nanosatellite, was already in danger of a collision. These types of situations occur much more frequently for larger satellites.
The problem of space junk is becoming increasingly important. The European Space Agency estimates that at the end of 2017, there were nearly 20 thousand pieces of debris with total mass of over 8 thousand tonnes remaining in orbit without control. They pose a threat not only to other satellites, but also to the astronauts on board the International Space Station.
How will our sail deploy?
The deorbit sail is a device which allows to shorten the time a satellite spends in orbit. The structure, which until now has been closed in a container 8 cm in diameter, will deploy after a Dyneema string burns up on signal from Earth. It will extend about 20 cm in half a second and unroll to the size 2×2 m. This will result in a drastic increase of the satellite’s drag coefficient and thus a decrease in its orbital velocity. Over time, the satellite will get lower until it burns up in the Earth’s atmosphere. According to our analysis, that should occur within 12 months. Without the deorbit sail the satellite would spend even 20 years in orbit.
The video below shows one of the tests of the deorbit sail conducted in a drop tower in Bremen in November 2017. It depicts the way the sail will open under the conditions in space.
How to follow this event?
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Translated by Krzysztof Zając – thanks a lot!