One year on - students celebrate the YES2 tether success
Today, one year after, the intriguing story of the second Young Engineers Satellite (YES2) experiment has reached its conclusion. After a lengthy investigation, European engineers are now confident that they have solved most of the mysteries surrounding the fate of the student mission.
Their in-depth detective work confirms that YES2 successfully deployed its tether to a record-breaking length and released a small capsule, known as Fotino, which re-entered the Earth’s atmosphere close to its planned trajectory.
On 25 September 2007, YES2 reached its climax when Fotino was sent plunging into Earth’s atmosphere. Since no signal was received from the re-entry capsule, engineers had to rely on indirect information from other sources. Preliminary data from YES2 obtained via the Foton-M3 mother craft suggested that the tether had not deployed to its full length, but a painstaking analysis has now shown that this was not the case.
Important clues were provided by data from three YES2 sensors that measured the speed at which the tether was deployed. When combined with detailed information about sudden changes in the orbit of the Foton-M3, it became clear that the tether had actually extended to its full length of 31.7 km before coming to a sudden halt.
Confirmation of this world-record-breaking tether deployment has come from various sources, including US radar tracking and other ESA experiments on the Russian Foton spacecraft. Of particular interest were the data from the DIMAC (Direct Measurement micro-Accelerometer) experiment, which provided invaluable information about shifts in the Foton’s acceleration and orientation.
“The DIMAC team passed their data to the tether experts at Delta-Utec, the company which managed the student work on the design and construction of YES2,” explained Roger Walker, YES2 project manager for ESA’s Education Office. “They were then able to analyse the peaks and shocks in acceleration at high time resolution and correlate this with the YES2 telemetry data.”
The DIMAC data show a short but large shock caused by the tether reaching its full length at almost maximum speed. This was followed by several periodic peaks in acceleration, indicating that the Fotino capsule was “bouncing” on the end of the tether as it swung underneath the Foton-M3 craft as planned. The tether and capsule were then released at the planned time, though its deceleration at release was slightly higher than expected, due to the greater-than-anticipated length of the tether.
“This caused the capsule to enter the atmosphere at a slightly steeper angle than planned, leading to a predicted landing short of the target area – either in the Aral Sea or north east of there, not too far from Baikonur from where it was originally launched”, said Walker.
“We don’t know whether it survived the re-entry, but – thanks to the efforts of Delta-Utec and everyone who provided us with the all-important data - we can now definitely state that it would have landed just within the designated landing zone in Kazakhstan.
“Coupled with the successes in deploying the longest ever space tether and in achieving the first ever de-orbit of a re-entry capsule using a tether, we can safely say that YES2 was a resounding success for the hundreds of students who worked on the project, a greater success than we first thought”, concluded Walker.
YES2 was one of the ESA-provided payloads on board the Foton-M3 microgravity mission. The Foton-M3 spacecraft and the piggybacking YES2 payload were launched by a Soyuz rocket from Baikonur, Kazakhstan, on 14 September. The YES2 experiment was installed on top of the battery pack of the Foton-M3.
The 6 kg Fotino capsule was attached to the end of a 0.5 mm thick, 31.7 km long tether. Once the tether unwound and deployment stopped smoothly at 30 km, the Fotino capsule was to be automatically released by a pyrotechnic device and sent on a return path to Earth’s surface through the atmosphere and landing safely by parachute in a pre-determined location. The objective was to demonstrate the ‘SpaceMail’ concept of delivering parcels back to Earth from an orbiting spacecraft using only a tether.
Almost 500 students from most ESA Member States and Cooperating States, together with the United States, Russia, Japan and Australia, worked on YES2. Although these were mainly involved in the preliminary design phase, nearly 200 students participated in the latter stages of developing and building hardware and software.
The ESA Education Office in the Directorate of Legal Affairs and External Relations has two education satellite projects already in development, including the European Student Earth Orbiter (ESEO), to be launched in 2010, and the European Student Moon Orbiter (ESMO), currently planned for 2011.