Young Engineers' Satellite 2

The Young Engineers' Satellite 2 (YES2) is a 36 kg student-built tether satellite that is part of ESA's Foton-M3 microgravity mission. The launch of the Russian Foton-M3 occurred on September 142007 at 13:00 (CEST) by a Soyuz-U launcher. The project was carried out by Delta-Utec SRC and supervised by the ESA Education Office and was nearly entirely designed and build by students and young engineers.

The YES2 mission took place 2007-09-25. The mission objective was to deploy a 30 km long and 0.5 mm thin tether in order to release a mini-satellite and re-entry vehicle called Fotino, the latter into a predetermined trajectory to a landing area in Kazakhstan. The mission was largely successful with the deployment was completed and the Fotino released as planned during a swing of the tethered system through the vertical (as seen from Foton). Due to an electrical fault, the on-board computer failed to register the final length correctly and only a partial deployment was reported to the press at first, based on telemetry available in real-time. Some weeks after mission completion, analysis of the full data set demonstrated that the tether deployed to its full length of 31.7 km. YES2 therefore established a new world record, as the longest artificial structure in space. The main contribution of the project has been the successful demonstration of a complex controlled deployment in two stages (necessary to obtain the required level of accuracy), and the large amount of data that has been recovered which helps to understand the deployer performance and tether dynamics in yet unseen detail (thanks to highly precise triaxial accelerometer data from a separate experiment on Foton). The small, spherical, lightweight reentry capsule, intended to demonstrate the SpaceMail concept, has not yet been successfully recovered. Calculations based on YES2 sensor data indicate that the landing site should be in or near the Aral Sea, which could explain the lack of beacon signal. Alternatively, the capsule, experimental in itself, may have burnt up or crashlanded.

The YES2 project

Most of the work done in this ambitious project (like design, manufacturing and integration) was done by students and young engineers. In total some 450 students participated.

Soon after the beginning of the project 5 so called "Centres of Expertise" were created. These were universities which were responsible for parts of the satellite or subsystems. The centres were: University of Samara, Russia (mission analysis, GPS); University of Modena and Reggio Emilia, Italy (re-entry capsule); Hochschule Niederrhein in Krefeld, Germany (tether); University of Patras, Greece (mechanical and thermal) and University of Kent, Great Britain. Coordination and system engineering was carried out by prime contractor Delta-Utec SRC from the Netherlands.

Towards the end of the project, in the manufacturing and integration phase, the work concentrated on the Delta-Utec office in Leiden and ESA's ESTEC in Noordwijk, where the satellite was build and tested.

The test program included:
* electromagnetic compatibility testing in the "Maxwell" EMC test chamber
* simulation of space environment in a thermal vacuum chamber
* vibration testing on a shake table
* functional tests of all components and sub-systems

The satellite was handed over to ESA at the beginning of May 2007 and was shipped to Samara (Russia) soon after, where YES2 was mated to Foton-M3 for the first time for test purposes. Afterwards YES2 and Foton were separated again and brought to Baikonur (Kazakhstan) by train where the whole satellite was completely integrated and mated with the launcher, a Soyuz-U rocket. Foton-M3 and YES2 finally launched on 14 September 2007 at 13:00 (CEST) from the Gagarin launch pad at Baikonur Cosmodrome.

Design of the satellite

There are three main components of the experiment:

*FLOYD – the YES2 deployment mechanism located on the Foton spacecraft;
*MASS – the Mechanical data Acquisition and Support System;
*FOTINO – a small spherical capsule, with a diameter of 40 cm and a mass of 6 kg.

YES2 mission design

During the flight, FLOYD would eject the other two components. There was then to be a controlled deployment of a 30 km long tether. Orbital dynamics would cause the Fotino capsule to be positioned in front of the mother spacecraft. By bringing the deployment to a halt, a pendulum-like swing would be induced. When the capsule and tether swung through the local vertical, the tether would be cut. Since the capsule would then be going too slowly to stay in orbit, it would begin to re-enter the atmosphere from an altitude of about 250 km, protected by a heat shield made of novel materials. Once it reached an altitude of 5 km, a parachute would deploy to ensure a soft landing on the steppes of Kazakhstan.

Links

* [http://www.yes2.info/ Homepage]
* [http://www.esa.int/yes2 ESA project homepage]
* [http://www.youtube.com/watch?v=7IN7mdU_QU4 mission animation]

References

* cite journal
journal=Nature
author=Katharine Sanderson
title=Dropping a line from space
volume=449
date=2007-09-26
page=387
doi=10.1038/449387a
* cite web
url=http://www.esa.int/SPECIALS/YES/SEMUI053R8F_0.html
title=YES2 team claims a space tether world record
date=2007-11-08
accessdate=2008-07-10