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Slide 1 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 OLYMPUS and the 1993 Perseids Lessons for the Leonids Doug Caswell OLYMPUS.

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Presentation on theme: "Slide 1 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 OLYMPUS and the 1993 Perseids Lessons for the Leonids Doug Caswell OLYMPUS."— Presentation transcript:

1 Slide 1 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 OLYMPUS and the 1993 Perseids Lessons for the Leonids Doug Caswell OLYMPUS Spacecraft Manager Applications Directorate Telecommunications Department European Space Agency, ESTEC, Noordwijk, The Netherlands

2 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 2 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 The early morning of August 12 1993 was predicted to be the peak of the Perseids Meteoroid Shower A colleague at work had said to me, the OLYMPUS Spacecraft Manager, that “OLYMPUS dies at midnight”, as I left work At 23:55 Zulu on August 11, the OLYMPUS Satellite lost earth pointing and began spinning By the end of August 1993, OLYMPUS had been put into a graveyard orbit and the spacecraft was safed and shutdown This presentation will reveal what we discovered

3 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 3 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 OLYMPUS was the largest civilian telecommunications satellite when it was launched in July 1989 Payloads included: Direct to Home TV for the BBC and the RAI Regular HDTV Transmissions Digital Broadcasting Specialised Business Services Ka band Services and Propagation Investigations

4 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 4 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Investigations were conducted by: British Aerospace, Prime Contractor GEC Marconi Avionics, Gyro Supplier Telespazio, Spacecraft Ground Control University of Kent at Canterbury, Impact Physics ESOC ESA, Ground Control ESTEC ESA, Programme

5 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 5 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Mission Background Launch, 12 July 1989 - last ARIANE 3 Earth Sensor Midnight Problem - Gyros used 6 hours per day Loss of South Solar Drive and Solar Array Power in 1991 Hardware problems and Operator error resulted in a frozen spacecraft and round-the-world journey - loss of fuel in 1991 Loss of North Solar Array Section in January 1993 Algorithms reprogrammed, Gyro use for midnight phase, no North/South Stationkeeping, Fixed South Solar Array, Limited Power, careful Payload Operations scheduling

6 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 6 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Operational Status prior to August 11 6 months of trouble free operation Plan was to continue operations for one more year Last year more customers and demonstrations than ever InterSatellite link to Eureca in LEO was demonstrated Sufficient fuel to perform the planned mission with allowance for reorbiting to a Graveyard Orbit But, no fuel margin for anomalies

7 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 7 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Preparations for August 11/12 Risk analysis performed for interception with stream NASA announced the delay of Shuttle Mission Reassessment of risk Microaccelerometer put in operation Additional support personnel sent to Ground Station Extra staff on alert for event support Payload operations performed as normal

8 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 8 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Anomaly Events: 23:32 Zulu Roll gyro spin down 23:40 Roll attitude diverged 23:53 Earth Presence lost (>15 degrees) 00:20 Automatic Reconfiguration Earth Sun Acquisition Safe Mode failed capture Spacecraft spinning about roll axis Anomaly in North Array telemetry for position Loss of Telemetry in Fucino for 7 minutes

9 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 9 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Operations: Spacecraft despin was not possible with biprop as monomethyl hydrazine was spun from outlet Operate system in cold gas mode to despin Spin rate reduced from 2.1 revolutions per minute MMH reprimed at.9 revolutions per minute Quick Thermal Gauging determined remaining fuels 3 Kilograms of MMH and almost no NTO Decision made to end mission and enter a graveyard orbit Final burn only lasted 38 seconds verifying fuel estimate

10 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 10 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Graveyard Orbit Following anomaly and despin, satellite was in an orbit with apogee 195 km below GEO and perigee 390 km below End of life tests were performed Final fuels and gas expended with apogee below 200 km Spacecraft electrically safed and telemetry turned off The OLYMPUS mission was over

11 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 11 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Investigations: Roll Gyro Turn Off Gyro turned on with no problems Difficult to fail only one of three operating gyros Spacecraft umbilical gave external access to gyros Umbilical interface uncovered Gyros operational during launch phase Tests inconclusive, roll gyro probably more marginal Probably spurious electrical event entering via umbilical

12 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 12 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Investigations: Microaccelerometer “Microphone”, listen for impact Nothing major in signal 7 events in 11 seconds were recorded 2 minutes prior to Roll Gyro shutdown Not correlated to onboard activity Impact on Solar Array would not be heard due to attenuation

13 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 13 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Investigations: Wheel Speed Pitch Wheel speed change due to Gyro run down Failure of Safing Mode Earth Sun Acquisition Mode should have captured Failure somewhere in control loops Most likely, short circuit in capacitor Possibly connection to space through sun sensor

14 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 14 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Investigations: North Solar Array position anomaly Problem disappeared, likely bit error Loss of Ground Telemetry Wrong position in ground antenna due to change of orbit Telemetry fringing effects due to spinning spacecraft Roll Thruster Firings Planned firings to desaturate wheels loaded by the fixed South Solar Array occurred a few seconds before Gyro off Exhaust gases would be in area of umbilical and sun sensor

15 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 15 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Investigations: Possible Perseid Impact Previous years about 50 meteoroids an hour for 2 to 3 days Peaking around 100 These visual meteors (magnitude greater than 6.5) mass of 1 mg or greater After 1988, peak about 400, predicted 10000 possibly 1993 Increased activity due to last close pass of Comet Swift- Tuttle in 1862 The peak occurred around 03:30 Zulu At 23:30 rate was 100

16 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 16 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Investigations: Possible Perseid Impact Sporadic Meteoroid rate is 10 Sporadics at approximately 20 km per sec Perseids about 60 km per sec For same visual magnitude, Sporadic is 100 times mass For the same mass, the Sporadic flux is 10 times Perseid Probability of impact is driven by Sporadic For equal damage however, similar probability Plasma production, 1 mg Perseids equals 50 mg Sporadics

17 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 17 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Investigations: Possible Perseid Impact At the time of “impact?”, the plasma risk was at least 5 times higher than normal Sporadic Sporadic impact rate is approximately 1.5 impacts per year of.1 mg particles OLYMPUS exposed surface area up to 140 m 2

18 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 18 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Investigations: Spacecraft Flux for Perseid Stream East58degrees1.94 sq. m. Westnil Southnil North342.89 Earth781.29 Aftnil South Array (fixed)738.48 North Array941.73 Most Probable Impact Area is Fixed South Solar Array

19 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 19 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Conclusions: We could not prove that the anomaly was the result of impact from a Perseid meteor, We did not hear it, We did not measure it on the wheels There was no apparent significant damage The impact seems most probable for dust intersecting the South Solar Array, generating a plasma which was augmented by the thruster firing in the area of the umbilical and the sun sensor which shut down the roll gyro and failed a capacitor in the safing control circuit. The rest is history when OLYMPUS had no fuel.

20 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 20 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Recommendations: For Meteoroid Showers, 1. Minimise cross section to Stream for peak period 2. Prepare operational contingency plans for recovery. Augment Support Teams 3. Set up to monitor for impacts 4. Protect from external plasmas through electrical windows (pre-launch) 5. Ground and cover all interface points such as umbilical(pre-launch) 6. If your spacecraft is weak and fragile, shut down the mission for the peak duration

21 OLYMPUS and the 1993 Perseids - Lessons for the Leonids Slide 21 Doug Caswell Leonids Threat Conference Manhattan Beach April 26/27 1998 Spaceraft are impacted by orbit debris, man-made and natural Some areas are very critical Larger spacecraft receive more impacts in their sweep of space Meteoroid storms have a bigger effect due to higher velocities Plasma is produced Large spacecraft should exercise caution during showers to minimise the risk Designs must be robust to this operational hazard Reference: Pages 139-150 International Journal of Impact Engineering Vol 17, Caswell et al 1995 0734-743X 95 S9.50-0.00


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