Student satellite mission a partial success

Photo: Liis Treimann / Postimees

Though impossible to overestimate as boost to popularity of science, the student satellite EstCube-1 sent into orbit in May 2013 failed in main aim of the project – testing the solar sail.

The 10-metre ever so thin cord, i.e. an electric solar sail, could not be stretched out of the apparatus due to failure in the motor supposed to unroll the thing. The satellite was supposed to test the idea by Finnish Meteorology Institute scientist Pekka Janhunen according to which space apparatuses may be propelled by cords thinner than hair, using the flow of charged particles issuing from the Sun.

Yesterday at Tartu County Tõravere Observatory, festively the active work of the cube was proclaimed ended. As the final Morse beeps sounded, the apparatus will now only be monitored, from time to time, as long as it is still capable to contact.

«Halloo, Earth, this is EstCube-1; I have worked in space for 651 days for mankind’s bright future,» stated the cube. «As of today (yesterday – edit) I’ll retire and, for the 20 years to come, will be reading your Valentine’s Day wishes. Long live Estonia!» Indeed, the last thing the satellite did was record Valentine’s Day messages by 4,000 people.

Within the days or weeks to come, its solar batteries – rapidly oxidizing due to the hostile environment – will be unable to produce power enough for the cube to be able to communicate with planet Earth. However, while no longer able to make contact, the thing will spin around the globe for some 23 years before sinking into the atmosphere and burning up.

The project was a success if only for the reason of the apparatus rising to the height of 650 kilometres and sending a signal back. Devices «Made in Estonia» were tested, and lots of scientific articles were written.

Citing Postimees, writing in October 2011: «The mission will be considered a success if succeeding to unroll from the cube satellite, in space, a ten metre aluminium nano cord – en electric solar sail – and to prove that, due to interaction of charge particles and the sail, the latter will push the satellite.»

Nanosail adventures

As the satellite was launched from French Guyana in May 2013, its team on Earth initially hoped to roll the nanosail out in mid-summer of that very year – at the end of August. At the end of December 2013, however, the programme initiator and supervisor Mart Noorma told Postimees that there was no need to hurry opening the sail and, as the preparations reach the right phase, the test would take place in 2014.

Also, Mr Noorma said back then that the initial prognosis that EstCube would be capable to work for a minimum of two years was coming true. Yesterday, he said the initial plan was for the satellite’s space technology to last at least a year in space conditions.

Last May, the media was told magnetism had occurred in certain parts of the cube. This, in turn, had an effect of the position of the satellite as interacting with Earth’s magnetic field.

The problem was due to cases around the cube’s batteries, and the bolts in the corners of its structure. Both contained iron and the magnetism caused by that begun to interfere. They had wanted titanium bolts to begin with, but time was short: not succeeding in obtaining titanium bolts, iron ones had to do.

By September, the young scientists still managed to solve the magnetism issue and get the satellite to spin at the record speed for nanosatellites – 2.3 rotations a second – which is a must to test a solar sail. Then, however, a much more mundane problem surfaced: the solar sail could not be unrolled from its spool as something had happened with its motor. By the way, the motor was not manufactured by our students, it was outsourced.

It would be highly unjust to call the EstCube-1 mission a failure to any degree; even so, it is honest to say it was a partial success, not a complete one. As told Postimees by the electric solar sail idea author Mr Janhunen, though the sail could not be unrolled the mission was still successful, and that not only in the popular scientific sense but scientifically so as well. Usually, the success rate of such tiny satellites is way lower than with the Estonians’ initial cube.

This year, the Finns are launching a satellite of their own which will also be testing Mr Janhunen’s sail. Now, the Estonians’ experience is used to increase the chances for the Finnish try to succeed.

Yesterday, Mr Noorma said goal No 1 was to build the satellite.

«In the history of student satellite programmes in the world, this usually is the most important goal,» he said. «After that, we are very happy if the satellite starts working in space at all. All alarm systems on board ought to stand the space conditions and display results.»

An important goal was to make the nanosatellite rotate in a controlled manner and at high speed, and in this they succeeded. The other aim was to see that, at high rotations, other alarm systems would keep working as well.

Thereafter, it was planned to do initial first tests of two solar sail components in space. One was an electron gun developed at Jyväskylä University, needed to charge the system. The other was the mechanical spool-like system for rolling the solar cord out.

«Succeeding in that, we also planned to measure effect of charged cord on atmospheric plasma,» explained Mr Noorma.

Thrice, the team succeeded in testing the electronic gun, proving that the technology worked.

«However, as we got the satellite rotating at the desired speed last September, and we started to roll out the cord, it never came out,» admitted Mr Noorma. «The next half year, the students were busy finding out what caused the systemic error. They determined that the rolling out mechanics did not stand the vibration at the launch of the satellite. A signal reaches the motor, but the motor will not rotate – probably, due to it having been mechanically broken.»

As also affirmed by Mr Janhunen, it was clear by September: the sail will not be rolled out.

New goals

Soon, the Estonians will be participating in new satellite programmes.

«The next mission is the Finns’ Aalto-1, one again testing the rolling out of solar sail; in that system the electronic board has been developed by Estonian students,» said Mr Noorma.

By the way, the Aalto-1 mission is led by an Estonian Jaan Praks, one to also start his career at the Tõravere Observatory.

According to Mr Noorma, EstCube also shot over 880 quality photos from the space. «Before EstCube-1, no other nanosatellite had shot such high quality photos from space,» he said.

Thus, within the European Space Agency education mission next year, a satellite a lot larger than the Estonians’ one will go into orbits, it’s camera systems again developed by Estonians. And: the camera mechanics are not developed at University of Tartu, but by students and supervisors at Estonian University of Life Sciences.

According to Mr Noorma, preparations are on for a couple of years for EstCube-2. «We have no financing partners, the mission is more expensive that EstCube-1, being also more complicated,» he explained. «The aim of the mission is to take the electric solar sail out of the Earth’s magnetic field into deep cosmos. This has not been done by any cube satellite, a very exciting challenge.»

EstCube-1 immediate benefits

• 19 Master’s degrees defended.
• 29 bachelor’s degrees defended.
• 25 Doctoral theses in the making.
• Four start-ups created.
• 12 scientific articles published (five more to come).
• 53 scientific reports presented.

Source: Mart Noorma