Rendezvous

This is the art and science of getting two orbiting object together. It is required for Docking with the ISS, repairing and retrieving satellites. To perform a successful rendezvous, the Space Shuttle crew must match the orbits and position of the ISS (or the target object, like the Hubble, etc.).

The Shuttle crew matches the orbits and location through a series of OMS/NC burns which match the Apogee and Perigee of the Shuttle and the target vehicle (The ISS or a satellite). After the burns series is completed, the last phase of the final “approach” of the rendezvous and docking with the ISS (or grappling a certain object in space) is performed manually, assisted by the radar guidance system and various cameras (and also by visually following the target through the Space Shuttle windows).

First stage of the rendezvous is figuring out where is the target object and how to match it's orbit to yours. This is pre-calculated by the GC weeks before the launch. In fact, the launch window in set according to those calculations.

The base if for all of these maneuvers is that lower orbits have faster “lap time”. They circle the earth faster allowing the intercepting object “catch up” with the target object. in our case the interceptor is the Space Shuttle while the target is a satellite or the ISS.
the Shuttle is launched to a lower orbit and every few orbits the peregee is raised by a few miles those “slowing” the closure rate (to raise the orbit you actually speed up), depends on the target orbit it usually takes three to five burns to get the orbits aligned.

All NC burns are made using the OMS engines.

After the NC burns are complete the Shuttle and the Target are a few miles from each other on very similar orbits. In SSM2007 the magic number is about 45Kft (or 22.5NM). Then the Shuttle maneuvers closer using its RCS thrusters. But in order to fine tune its orbit the Shuttle needs exact information on the whereabouts of the target. To give the crew this information the Shuttle is using two systems, the Star Tracker and the KU band Radar. Both controlled from CRT4 in the R11 panel.

In addition for its duties and a navigational aid the Star tracker can help determine the location of other orbiting objects. It just needs to be activated to do so by the crew. The star tracker controls are available in the OPS2 Mode of the The GPC under the SPEC22 display.

In order to load a target TGT TRK needs to be enabled on both Y and Z axis, this is done by selecting ITEM 5 (Y) & ITEM 6 (Z). After setting the star tracker to the correct mode - targets can be loaded using ITEM 11 and ITEM 12 one per axis. The correct syntax for loading a target includes the target ID in the The GPC - so you are actually typing ITEM 11+2 EXEC (or in GPC free-speech “Load -Y target No.2 - GO”)

Loading the target allows the Star tracker to calculate azimuth and elevation as well as give a rough range estimate. This information is then fed to the KU-band radar.

The KU-band antenna is usually used for high-Bandwidth transmissions back to earth. But it is also used as a radar antenna. The KU-band controls are available in the OPS2 Mode of the The GPC under the SPEC33 display. In order to function for the rendezvous it should be activated in RNDZ NAV mode (ITEM 1).

The computer will automatically try and aim the antenna at the target selected by the Star-tracker. This is the software side of the work. The antenna itself should be allowed to track and the radar should be turned on. This is done from the A1U panel.

The KU-band Power should be moved to the ON position and the KU-band mode selection rotary dial should be set to Auto Track

The final most important part of the rendezvous is done with the Line-Of-Sight indicator (LOS). This indicator displays the information supplied by the KU-Band Radar. it allows the crew to have range, closure rate, elevation and azimuth offset and drift rates all displayed in a relative simple matter. The indicator is found on the A2 panel. LOS contains two indicators a Digital readout and an Analog display.

The LOS work mode is set my two switches.

• DIGI DIS SELECT - allows the crew to display ether Range and closure Rates (R/R) or Azimuth and Elevation deviations (AZ/EL).
• PNTR SCALE - changes the resolution of the analog display - the X1 is more sensitive then the X10 therefor it is used to fine-tune the approach as you get closer to the target object.

In order to rendevous with your target you should make sure that you are closing in, done by translational thrust toward the target. Closing in means you have a negative number on your lower digital read out when DIGI DIS R/R is selected. In SSM2007 this rate should be kept at >3.00 to meet your target in time. In most cases you are not moving exactly towards the target when starting the final rendevous maneuver. The “needles” on the analog display show if you should move the shuttle to the right/left (Azimuth) or up/down (Elevation) to approach the right path. DIGI DIS should be switched to AZ/EL for this case. It might take some longer translational thrusts “toward” the needles. If the digital readouts on the right start to decrease you are on your way to the correct path. If the needles are perfectly centered, the readouts should be at or near zero. Now keep it centered and control your closure rate and distance once more by switching DIGI DIS to R/R and back.

Rendezvous Video Tutorial

Same Video Tutorial on Youtube:
Part 1 Part 2 Part 3 Part 4