PARIS — Satellite fleet operator Intelsat has raised concerns that an earlier story here — http://bit.ly/2vE7o93 — left the impression that the IS-33e satellite might be unable to serve its customers because of an anomaly with its attitude-control system.
This is not the case.
IS-33e has suffered two fuel-related issues. The first occurred just after launch in August 2016, when the main orbit-raising thruster malfunctioned, forcing the satellite to spend extra time and fuel to reach its final orbit. IS-33 arrived at its operating station in late January.
The second anomaly, discovered in February and not previously disclosed, involves an unexpectedly high consumption of hydrazine fuel by the satellite’s attitude-control thrusters during routine north-south stationkeeping (NSSK) maneuvers.
Intelsat in March filed an insurance claim for $78 million to cover both issues after making an assessment of the consequences in consultation with satellite builder Boeing Satellite Systems International.
Some insurers have agreed to pay their share of the full claim; others are awaiting more information.
Intelsat now expects IS-33e to perform all its functions for slightly more than 11 years, rather than the 14.6 years of fuel life estimated at the time of the launch aboard an Arianespace Ariane 5 rocket. Customers should see no effect on the satellite’s performance during this period.
To clarify the issue, Intelsat agreed to answer questions about the failure and its consequences.
IS-33 reached its final position in January. When was the first NSSK maneuver?
Also in January.
When did you and Boeing conclude that these operations were using an excessive amount of fuel?
In February, we noticed that the maneuvers were using more fuel than should be the case. The thruster, located near the solar array, emits a plume that is larger than anticipated, creating a disturbance torque between the arcjet and the solar array, which needs to be compensated by the firing of other thrusters.
We made our claim to the insurance underwriters in March, encompassing both these issues. Nothing has changed since. There have been no new issues.
Is the Boeing 702MP platform able to gauge fuel levels precisely?
Yes, there is a very precise propulsion flow model that looks at many parameters and the expected performance of each, and then you compare it to actual performance to assess fuel use.
Why are you launching the same model satellite before Boeing has produced a final report and conclusion on the anomalies?
We understand the issue, and put corrective measures in place for follow-on spacecraft. As part of the standard process, mitigation steps are implemented for issues that arise on prior spacecraft and this is no exception. Mitigation steps are already implemented on Intelsat 35e and Intelsat 37e and we have allocated sufficient fuel to control spacecraft attitude during north-south station-keeping maneuvers.
So you are confident that even without a root cause, Boeing has surrounded the problem well enough to prevent a recurrence?
That’s right. And we have made allowances for future satellites in terms of fuel consumption to accommodate this and meet our operating life goals. It’s not so different from what we do normally. Once a satellite shows its ‘signature’ in operations, we implement mitigation steps in preparing for the next satellite of the same model.
Your insurance claim is based on estimates of fuel depletion over a decade. Does this assume a constant rate depletion with each NSSK maneuver over the next 11 years?
The issue is continually experienced, but of course the effect of the anomaly varies over time as the mass of the satellite changes. We conducted a very comprehensive interaction assessment of the arcjet and the solar array in early February, and we developed a flight-correlated satellite model.
Our prediction is based on utilizing the measured data with known propagation of mass property changes as fuel is consumed to assess the fuel consumption over life. Hence, it is a high-fidelity assessment. The arcjet issue accounts for less than 10% of the total expected loss of satellite life. The policy deductibles (inclusive of service life) govern what you are allowed to claim under the policy. We are seeking an 18% loss claim once you get through the deductibles.
The total impact is roughly 3.5 years, inclusive of the two issues. We originally planned for 14.6 years and we now will get 11.1 years.
Some insurers apparently aren’t convinced.
We are satisfied that our claim is justified. A significant number of insurance underwriters are in agreement with our interpretation of the policy. Negotiations are still ongoing with others.