YES Ejection from TEAMSAT box
Edited from design drawing by A.E. Bradford
Delta-Utec is the initiator of the Young Engineers' Satellite (YES),
a satellite full of experimental technology for space applications, built
at record low cost in extremely short time by young engineers and students. It was proposed
October 1996 at the IAF in Beijing and then supported in writing by e.g.
Arthur C. Clarke.
1 Year later YES had already been launched
on the Ariane 502 qualification flight as a part of the ESA/ESTEC scientific
payload TEAMSAT. In an extremely short time-frame over 40 young engineers
and students from 10 European countries have built a satellite with the
help from experienced ESA people.
Among others, YES carries a GPS receiver and the longest
structure ever brought into space: a 2x35 = 70 kilometer tether!
A paper on the YES satellite and the tether experiment was presented (before
launch) on the Tether Interchange Meeting in Huntsville Alabama and can
be downloaded here.
A simulation of the tether deployment can be downloaded here.
A detailed paper in two parts:
1. YES and its experiments (including mission and results)
2. Managing YES (including failure analysis & lessons learned),
presented at the IAF in Amsterdam
can be downloaded here.
Some first YES mission results:
The successful YES mission was completed the 3th of November
1997. Below are presented the first draft results of the YES experiments
.
GPS
In orbit 5 we received a GPS signal from 'the other side of the world".
Also 12 Signals were received above GPS constellation!. However the data
analyses show that these 12 signals are most probably wrongly interpretated
by the GPS receiver due to RF interference. As this homepage is intentionally
left short we kindly refer to a thesis report of Martin van de Pol: "
The implementation of a GPS subsystem on TEAMSAT (mail us)"
The monitoring display shows the received GPS satellite number, the Doppler
shift and the signal to noise ratio (S/N). The low S/N ratio is typical
for the apogee pass where the GPS receiver searches for satellites on the
'other side of the earth'. The doppler shift measured in orbit is 5 times
higher than for terrestrial applications.
PC104
This commercial technology experiment has been shown to perform flawlessly
for at least 35 hours in the space environment, passing the Van Allen belts
9 times. At the moment of last contact, the conditions inside the PC were
still nominal.
Also pictures have been successfully taken with the commercial QuickCam
camera attached to the PC104. They showed no signs of radiation degradation.
RADFET & Scintillating Fibre
Both these radiation experiments have been operating continuously during
YES operations and produced a nominal amount of data. The RADFET data was
used to verify the new Scintillating Fibre technology tested for the
first time in space and both experiments gave cross reference of the
radiation environment in the altitude range to 26000 km.
Data has been processed by the PI. The TEAMSAT homepage contains
more data!
Sunsensors
The sunsensors developed for YES have been used throughout the mission
for real time attitude estimation and as such they have proved to be very
useful to determine the rotation of TEAMSAT after injection in its off-nominal
orbit and attitude.
JORIS on-board computer: a story of amazing design and successful redundancy
YES carried 3 totally different computers, each linked communicating with
eachother and with an overlapping subset of the experiments for redundancy.
Unfortunately, the most able and complex of the 3 YES on-board computers
and responsible for e.g. data storage, delayed commands and hardware control,
developed for YES by Delta-Utec stagiaires in record time and at record cost, was put into an eternal
boot-loop after download of a faulty software version just days before launch.
The software version was not tested on the engineering model due to time pressure
since the YES team was undermanned at the Kourou launch site at that time.
The computer did not revive. It was supposed to measure accelerations during different phases of the mission, take pictures
with one of the QuickCams and autonomously operate the GPS during communication black-outs.
It also provided YES with 40 MB of storage capability. Finally, it was designed to operate the 35 km tether deployment.
The tether deployment was cancelled before flight when the launch authority changed the nominal Ariane orbit: in the new orbit configuration a deployed 35 km tether would mean a hazard to satellites in LEO.
One datapoint from this computer is that the operations of YES indicate that
the watchdog circuits in JORIS, carrying their own battery, worked perfectly
in orbit conditions.
As the JORIS development has attracted interest from industry
for follow on missions (its technology has since been successfully used for e.g. the TSE deployment test rig),
an engineering model has been running in parallel to the mission inside the Experiment Control Center (ECC), performing the main mission stages as expected
and reacting well to the telecommands that were planned for the YES mission.
Part of the GPS functionality could be successfully recovered using the engineering model (EM) on the ground: JORIS EM, while inside the ECC, was set up to process GPS data coming down from the YES in orbit, thus taking over the functionality of the unit on-board, automatically responding to the GPS unit, preparing commands, which were then sent up again to the YES GPS.
Saying goodbye to the living result of a year of intense and wonderful work
Apart from the pre-flight failure of the JORIS flight unit, the YES team had to cope with another disappointment: the YES was misoriented in space 90 degrees off-nominal, causing the transponder to heat up more and more and finally break down. Communication with YES could not be established around time of ejection where the second part of the YES mission would
have commenced. YES has been ejected, into an orbit with
approximately the same period: pictures from AVS and VTS taken during TEAM
bonus time, one orbit after ejection in apogee, show
YES approaching the TEAM within tens of meters saying goodbye before disappearing
again forever: TEAM finally gave up one apogee later as planned when the batteries were depleted, having successfully performed oxygen flux measurements, CMOS imaging (of separation and others) & autonomous star sensor operation, closing the activities of a pair of satellites built through an unprecedented successful approach through the inspirational force of Young Engineers.