The launch vehicle consisted of a Titan IVB booster and an Inertial Upper Stage. Nominally, the Titan booster takes the IUS and the satellite into a low earth orbit, approximately 200 miles above the Earth, and then separates the IUS and satellite. The IUS then takes the satellite to its final geosynchronous orbit, approximately 22,000 miles above the Earth.

The IUS uses two solid rocket motors to take the satellite to the higher orbit. Stage 1 or SRM 1 transfers the satellite from low orbit to the higher orbit. Stage II or SRM 2 injects the satellite into the intended circular geosynchronous orbit.

A review of the data indicates an anomalous event occurred at the time IUS Stage I and Stage II were to separate. The timeline of events is as follows:

At T+8 minutes after lift off, the Titan IVB booster separated from the IUS. Indications are that the IUS and the satellite were placed in the required low earth orbit. Approximately 1 hour and 15 minutes after lift off, the IUS SRM 1 fired to initiate the transfer orbit. Indications are that SRM 1 performed as expected.

At 6 hours and 30 minutes after lift off, Stage I and Stage II of the IUS were scheduled to separate. Data shows several anomalous events occurred during the separation sequence. Specifically, although two separation break wires indicate separation had occurred, a separate connector continued to carry signals, indicating the separation was not complete.

Under normal conditions, Stage II extends a compressed nozzle called the extendable exit cone after separation. When the extenders reach a certain pressure they swing away or disengage and that is taken as a signal that the cone is fully extended. In this case, one of the extenders disengaged within 2 seconds after receiving its command. Normally, the expected duration for a full extension is 7 to 8 seconds. The other two extenders did not indicate full extension until after SRM 2 fired.

Telemetry then shows large pitch, yaw, and roll attitude errors occurring after SRM 2 was fired. In effect, the data shows the vehicle and satellite tumbling in their transfer orbit.

The stack attempted to regain control, but failed to do so. The satellite was separated from the IUS second stage, but remained in a complex tumble in a highly elliptical orbit. The difficult task now is to determine precisely what happened and why this sequence of events occurred.

We have a team of experts at Boeing's facility, the manufacturer of the IUS, in Kent, Washington evaluating the data. At this time, it is unknown how long it will take to complete the investigation.

MilSpace - SpaceDaily Special Report

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