Tim Furniss/LONDON
A Chinese Long March 2C/SD booster is poised to launch two more Iridium mobile communications satellites into orbit this month or in early 1999, bringing to 86 the number of spacecraft so far sent on 18 successful launches since May 1997.
Motorola's flagship project, which is three satellites short of the minimum complement of operational and back-up satellites in six orbital planes, is apparently going well. But despite the successful launch campaign so far, 10 of the 84 satellites in orbit have failed and two others are on the brink of being written off.
To the space industry, the Iridium case must be of some concern. That one in eight of the spacecraft has failed is not a particularly good record, but apparently Motorola feels comfortable with this rate of attrition, saying that it expects to suffer six failures a year as it maintains the satellite system.
The insurers of the Iridium system are certainly not comfortable. London-based space insurance broker Crawley Warren (part of International Space Brokers) is dealing with claims for $177 million for the loss of three pairs of satellites and is waiting for another $59 million claim for the loss of two more satellites to land on its desk.
It is understood also that another claim for $18 million was successfully lodged. This related to the damage of one satellite during a launch, bringing the number of failed craft to nine. Three other satellites have also suffered anomalies.
It seems that Motorola is prepared for some losses. Perhaps the insurance community would be forgiven for feeling dismayed about this apparently acceptable loss rate. Iridium itself is not concerned. "We designed the system with projections for possible individual failures," the company says. Insurers claim that the number has surpassed those failure projections," it says.
The real concern about the losses must be questions asked about quality control on "production line" satellite systems involving so many spacecraft, as this should have ramifications for future multi-satellite systems and their insurance cover. One of the largest growth markets in the satellite communications industry will be that of mobile and multimedia spacecraft constellations in low and medium earth orbit.
The Iridium system is designed to operate 72 satellites in low polar orbit, divided into six planes each containing 11 satellites, plus one spare. The imminent Long March launch will place two more satellites into Plane 2, which has suffered three confirmed failures, with another craft experiencing an anomaly .
"The in-orbit insurance cover is believed to cover each plane with a one-satellite deductible for odd numbers of failures," says David Todd, space analyst at Airclaims of London. "So, if three fail in a constellation, the claim will be for a pair unless another failure causes two pairs to be made up". The biggest concern must be that eight of the 12 Iridiums that have malfunctioned have been victim of failures in the spacecraft's attitude and orbit control systems, part of the LM700 spacecraft bus supplied by Lockheed Martin, although the US company defends its equipment.
"There is no design level problem with the LM 700 Iridium bus," it says. "Each of the satellites that has suffered a catastrophic loss has done so for reasons that are not attributable to the bus design. Satellite attrition was planned for in the design of the system. That is why Motorola has the option to purchase up to 149 satellite buses up to 2005 to replenish the constellation as needed. The fact is that the replacement of the spacecraft is in the plan of operations for the constellation.
IRIDIUM SCORECARD (WITH SATELLITE NUMBERS ) Some data drawn from Airclaims SpaceTrack datasbase
(All 1998 unless stated)
ORBITAL PLANE 1 - 12 operational
Launch 13. Proton K. 7 April
62, 63, 64, 65, 66, 67, 68.
Launch 16. Delta II. 17 May
70, 72, 73, 74, 75.
ORBITAL PLANE 2 - 10 operational
Launch 4. Delta II. 21 August, 1997
22, 23, 25, 26, 24 attitude and control orbital systems (AOCS) failure - loss.
Launch 9. Delta II. 20 December, 1997
45, 46, 47, 49, 48 AOCS three-axis gyro assembly malfunction - partial failure.
Launch 14. Long March 2C/SD. 2 May
69 AOCS failure. 71 Primary link system failure - loss.
Launch 15. Long March 2C/SD. 2 May.
3, 76.
ORBITAL PLANE 3 - 11 operational
Launch 5. Proton K. 14 September, 1997
27 AOCS failure - thruster -loss, 32 communications fault preventing link with other satellites - partial loss, 33, 28, 29, 30, 31,
Launch 12. Delta II. 30 March
55, 57, 58, 59, 60
ORBITAL PLANE 4 - 12 operational
Launch 1. Delta II. May 5, 1997.
4, 5, 6, 7, 8.
Launch 6. Delta II. 28 September, 1997
19, 34, 35, 36, 37.
Launch 11. Long March 2C/SD. 25 March 51, 61.
ORBITAL PLANE 5 - 14 operational
Launch 2. Proton K. 18 June, 1997.
9, 10, 12, 13, 16, 11 AOCS failure - momentum wheel - loss, 14 antenna fault - partial loss .
Launch 10. Delta II. 18 February
50, 52, 53, 54, 56.
Launch 18. Delta II. 5 November
2, 83, 84, 85, 86.
ORBITAL PLANE 6 - 13 operational
Launch 3. Delta II. 9 July 1997.
15, 17, 18, 20 AOCS failure - momentum wheel - loss, 21 communications payload allegedly caused by damage from falling object inside payload shroud of Delta II during launch - loss.
Launch 7. Delta II. 9 November, 1997.
38, 39, 40, 41, 43.
Launch 8. Long March 2C/SD. 8 December, 1997
44 AOCS failure loss, 42.
Launch 17. Delta II. 8 September 77, 80, 81, 82, 79 AOCS failure - loss.
SUMMARY
Total operational : 72. Total launched: 84. Failures and malfunctions: 12.
Insurance claims: four covering seven craft - $59million claims for 20 and 44, 11 and 14 and 24 and 71. $18 million claim for 21. Total claims: $195 million. $59 million claim expected for 69 and 48. Outstanding anomalies: 27, 79, 32
Source: Flight International
