Soyuz Launches Progress Cargo Flight to ISS / Automated Rendezvous Tests

A Soyuz U successfully launched Progress M-46 from Baikonur Cosmodrome, pad LC1/5, at 0536:30 UTC on June 26. The cargo spacecraft is carrying 2.5 metric tons of supplies, including propellant, oxygen, water, food, medicines and packages, to the International Space Station (ISS) for the fifth expedition crew. The spacecraft was injected into a 193 km (104 nmi) by 245 km (132 nmi) orbit, inclined at 51.6 degrees. Progress M-46 is expected to dock to the aft end of the ISS Zvezda service module about 0625 UTC June 29. At 0826 UTC on June 25, Progress M1-8 undocked and was spring-ejected from ISS carrying trash and unneeded equipment, burning up in the atmosphere about four hours later.

Russian flight controllers plan to use the cargo spacecraft to perform tests on the KURS automated rendezvous system. The test adds an extra day to the timeline, so instead of the usual two-day transit from launch to docking, the trip will take 3 days. Several previous automated rendezvous missions have exhibited a phenomenon referred to as 'antenna switching,' so the Russians want to investigate the behavior. The Progress will be positioned 30 km behind the station in a slightly higher, about 1 km, orbit, so it will appear to have a negative velocity vector. Over the day of testing, it will lag slightly further behind the station. ISS will be placed in a sun solar inertial reference attitude so that from the perspective of the Progress spacecraft the station will appear to rotate 360 degrees. As this is happening the automated rendezvous systems will be activated and monitored by the Russian flight controllers to see if the ‘antenna switching’ phenomenon occurs, gathering data and troubleshooting the situation. Progress will stationkeep for a day or so before initiating the nominal rendezvous phase for the Progress using its automated systems. The Russians will use a full day for testing so they can get coverage over their full complement of ground sites.

This cargo flight comes in the wake of a grounding of the shuttle fleet on Monday, June 24. Recent inspections of Space Shuttles Atlantis and Discovery revealed cracks, measuring 0.1 to 0.3 of an inch, in one flow liner on each of those vehicles. Some of the cracks were not identifiable using standard visual inspections and were only discovered using more intensive inspection techniques. A dozen lines through which chilled hydrogen and oxygen flow will be inspected on each of the shuttle. The liners in the fuel lines of the Columbia, the first shuttle, are made of stainless steel, while those in the others are made of Inconel, a nickel-chromium alloy. A prolonged grounding of the shuttle could disrupt ISS assembly missions and other time-critical operations with. three of the four shuttles assigned to transporting crew and supplies to the station. Though this is an indefinite suspension, Columbia, STS 107, the next scheduled flight will likely be delayed only until sometime in August.

NASA has a procurement under way, Alternate Access to Station (AAS), seeking studies to carry cargo on U.S. indigenous systems, should the shuttle be grounded. The AAS studies should be awarded shortly, leading to the selection of an alternate cargo service in about a year, with first flight possible as early as 2006. Currently, other than shuttle,  Progress spacecraft offer the only way to supply the station, though development of cargo spacecraft is underway by Europe, ATV, and Japan, HTV.

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