Progress undocked – EAS update

by Chris Bergin

The Russian Progress resupply ship (M-55/20P) has been successfully undocked from the International Space Station (ISS) Monday – and has been disposed off over the Pacific Ocean.

Progress 21P remains docked to the station, with Progress 22P due to launch to the ISS on June 24, carrying fresh supplies ahead of Shuttle Discovery’s arrival early in July.

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The Progress undocked on schedule (10:04 EDT time) and performed nominal separation and deorbit burns for its re-entry and burn up in the atmosphere.

NASA’s On-Orbit report (available daily on L2) for the day’s events noted: ‘After its undocking by spring force at ~0.12 m/s and subsequent separation burns (two required this time because of near-nadir undock attitude), 20P passed ~2300m below the ISS at 10:28am (overtaking it), performed its deorbit burn (delta-V: 85.1 m/s) at 1:06-1:08pm, and re-entered the atmosphere over the Pacific Ocean at ~1:41pm. Splashdown of surviving pieces was at about 1:53pm.

‘For the undocking, ISS attitude control was handed over to Russian MCS (Motion Control System) at ~8:15am and returned to U.S. momentum management at ~10:35am, still in earth-fixed LVLH (local vertical/local horizontal).

‘During the undocking, the station was in free drift for ~9 min. Structural response data were taken by MAMS (Microgravity Acceleration Measuring System) and the external truss-mounted SDMS (Structural Dynamic Measurement System).

‘The undocking was preceded at ~4:10am by a temporary shutdown of the amateur radio equipment in the FGB (Ericsson) and SM (Kenwood) to prevent radiofrequency interference with the departing Progress vehicle.

The undocking freed the DC1 Docking Compartment port for Progress 22P, which is due to dock with the ISS on June 26.

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In related ISS news, the Early Ammonia Servicer (EAS) tank that is set to be jettisoned off the P6 truss during STS-118’s mission, is not exclusively due to it obstructing the relocation of the truss segment it currently occupies, ahead of further assembly and relocation missions. Its certified structural lifetime is the defining reason, according to NASA.

‘The jettison is an option that we are evaluating for the hardware because of structural life of the hardware itself, not a physical interference with moving P6,’ noted NASA’s Kylie Clem, International Space Station & Mission Operations Directorate Public Affairs Specialist, to this site. **EAS Article**

‘The EAS was certified for an on-orbit life of five years which will run out this fall. Engineers are evaluating extending that for one more year as we work on a plan to safely remove it and return it or jettison it.

‘The timeframe we are currently evaluating is the 13A.1 stage. We originally planned to return it on shuttle when it was no longer needed. Other options are being discussed because of the limited number of shuttle flights remaining and considering it will have reached its certified structural limit.

‘It was put in place to service the early external active thermal control system and the photovoltaic thermal control system in the event either system had a leak. If there was a leak, a spacewalking crew would perform the necessary repairs or reconfigurations and then use the EAS to refill the cooling system with ammonia.

‘It has not been needed to this date and will no longer be necessary once the cooling system is transitioned to the permanent system during shuttle mission STS-116/12A.1.’

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