NASA managers are investigating a proposed plan that would see a Soyuz spacecraft undock from the International Space Station (ISS) during the upcoming STS-133 mission in order to take photographs of the orbital outpost, along with its record number of attached Visiting Vehicles (VVs) and the docked Space Shuttle Discovery.
A Family Portrait:
During the STS-133 mission, currently planned for late February/early March, the ISS will have a larger volume and a greater mass than it has ever had before.
Since the most recent Space Shuttle ISS flyaround – which was during the STS-132 mission in May 2010 – the ISS will have five major new additions: Japan’s H-II Transfer Vehicle-2 (HTV-2), Europe’s Automated Transfer Vehicle-2 (ATV-2), the Permanent Multipurpose Module (PMM), ExPrESS Logistics Carrier-4 (ELC-4) and Shuttle Discovery.
The STS-133 mission will be the last and only opportunity to photograph ISS in this unique historical configuration.
This would not be the first time that a Soyuz has been undocked in order to provide a vantage point for Shuttle photography. During the STS-71 mission in June/July 1995, a Soyuz undocked from the Mir space station in order to photograph the undocking of the Space Shuttle Atlantis.
Mir was uninhabited for a brief period while both the Shuttle and Soyuz were separated from the station. Mir’s control computers went down during this period, causing the Soyuz crew to speed up their re-docking before Mir built up rotational rates due to its loss of attitude control.
The plan to undock a Soyuz during STS-133 was first suggested by NASA Headquarters in Washington DC. The suggestion led Mission Operations Directorate (MOD) to conduct a short-notice study into the proposal at the Johnson Space Center (JSC) in Houston.
Three options were considered to carry out the proposal. Option 1 was to have the Soyuz undock from the ISS, photograph Discovery and the ISS, then conduct the de-orbit burn as normal and return to Earth earlier than planned.
Option 2 was to have the Soyuz undock, perform photography, then re-dock to ISS, thus requiring the use of dual-docked operations (due to a Soyuz docking while the Shuttle is present). Finally, Option 3 was to have the Soyuz undock and take photos, then undock the Shuttle, and then re-dock the Soyuz to the ISS (similar to the process used on STS-71).
Prior to the MOD meeting at JSC, it was decided that Option 2 would be pursued. Option 1 was not chosen because the impacts of bringing the Soyuz home and ending Increment 26 early were too great. Option 3 was dropped because not enough time exists (only 2 weeks) to conduct trajectory analysis for proximity operations between three spacecraft (ISS, Soyuz and Shuttle).
The details of the undocking and photography procedure were outlined in an overview presentation, available to download in full on L2.
Click here for ISS news articles: http://www.nasaspaceflight.com/tag/iss/
Soyuz TMA-01M/24S, which launched to the ISS on 7th October 2010, will be the Soyuz that will perform the manoeuvre if approved. 24S, docked to the Mini Research Module-2 (MRM-2) Zenith port, is the first of the new “Digital” Soyuzes.
The 24S crew would consist of Russian Cosmonauts Alexander Kaleri and Oleg Skripochka, and US Astronaut and ISS Commander Scott Kelly. 24S would undock from MRM-2, perform the flyaround manoeuvre, and then re-dock to MRM-2.
A number of options are being considered with regard to the manoeuvre itself, all of which were outlined in another presentation acquired by L2.
The first – most basic, and therefore least risky – option being considered would be to treat the manoeuvre as a standard fly-around to another docking port, a manoeuvre that has been demonstrated many times on ISS.
For this manoeuvre, the Soyuz would back out to 35m from the negative R-bar, as is done on standard relocations. The R-bar, or Radius-bar, is an imaginary line between the ISS and the centre of the Earth.
This procedure would enable the Soyuz crew to gain a 124 degree Field Of View (FOV) of the Zenith side of the ISS, viewed from the Soyuz’s forward-facing window (124 degrees is the maximum FOV that can be gained from the forward-facing window).
The Soyuz crew would photograph the ISS using hand-held digital cameras.
The second manoeuvre being considered is the same as above, but with the ISS rolled 15 degrees on its side. This will enable a better view of the ISS’s Nadir modules and VVs. The 15 degree roll fits within the analysed Torque Equilibrium Attitude (TEA) envelope.
The third manoeuvre being considered is to have the Soyuz back out to 200m on the negative R-bar, which would allow for a full view of the ISS from the Soyuz forward-facing window.
The fourth option would be the same as above with the ISS rolled 15 degrees. The fifth option is again the same as above, but with the ISS rolled 45 degrees instead of 15. This would allow for a much greater view of Nadir modules/VVs. However, the 45 degree roll manoeuvre falls outside the TEA envelope.
The sixth option would be to fly the Soyuz to a range of 200m from the ISS, also flying the Russian vehicle 45 degrees above, 45 degrees behind, and 45 degrees out of plane from the ISS (approximately 115m in each axis). This would allow for a partial Zenith and partial side view of the ISS from the rear perspective.
For this manoeuvre, the Soyuz would need to fly out of the ISS’s solar array envelope, and then fly around to the viewing point.
In all, the entire operation would be a 15 hour procedure, consisting of eight hours of Soyuz preparation, activation and hatch closing, one hour of undocked operations, and six hours of Soyuz leak checking, hatch opening and deactivation.
Many preparations and On Board Training (OBT) events would need to be conducted prior to the flyaround, including a three hour Soyuz descent drill and a three hour photography drill for the 24S crew. A one hour, one crew member Soyuz Motion Control System (MCS) test would need to be performed, with Mission Control Center (MCC) assistance.
Items may also need to be transferred between 24S and the ISS prior to the undocking. In total, the preparation would take six hours of CDR Kelly’s time during the STS-133 mission.
If the 24S crew had a nominal sleep pattern on FD-8, then they would get a four hour nap prior to the undocking and flyaround. Alternatively, a five hour sleep shift could occur on FD-8, with a nominal sleep duration. If this were to happen, then CDR Scott Kelly would be unable to perform his scheduled PMM tasks.
Many other 24S crew tasks would need to be rescheduled, deferred or reassigned to other crewmembers, including PMM flag signing, crew conference, crew picture, face in space, nitrogen and oxygen transfer, scientific experiments and a PAO event.
Also, the Soyuz hatch opening would occur only 2 hours before the hatches between Discovery and ISS were closed for Discovery’s departure on FD-10, meaning that the 24S crew may be unavailable for farewell and hatch closure activities due to their Soyuz deactivation work.
Alternatively, a new FD-9 could be inserted into the STS-133 timeline, thus extending the STS-133 mission by one day. The major benefit of this option over the above option would be that the Shuttle and ISS crew could be performing PMM Intravehicular Activity (IVA) tasks while the flyaround was on-going. Also, FD-10 and 11 (previously FD-9 and 10) would remain unchanged.
The flyaround plan is currently far from certain, as NASA are still awaiting inputs from the Russian space agency, Roscosmos, on the flyaround plan.
However, STS-133 will be the last and only chance to photograph the ISS in all its glory, complete with its parent, the Shuttle, and its children, the fleet of VVs. The views would undeniably make for some beautiful photographs that would be a fitting tribute to the Shuttle, while enthralling the space community for years to come.
STS-133 Specific – Including ET Stringer Issue – Articles: http://www.nasaspaceflight.com/tag/sts-133/
(Images via NASA Presentations (L2)/L2 Historical Images)