The displays required for this are varied, then, from planning the actual deorbit burn, to monitoring the execution of the burn (see the Orbit FDO displays), to the evaluation of the real-time entry and landing trajectory across multiple scales.
Of all the FDO displays, the groundtrack plots nearest the end of the landing phase are the most understandable and perhaps some of the most publicly recognizable of anything presented here.
Feel free to contact me if you have any questions about anything you see here!
Deorbit Opportunities
The Deorbit Opportunities Processor (“DOPS” for short) is used by FDOs in all phases of the mission. It provides the FDO with a list of potential upcoming entry opportunities for a variety of landing sites.
This particular display example is referred to as the Deorbit Opportunities Table (“DOT”). It is the primary summary for Continental US (CONUS) landing opportunities to Edwards AFB (EDW), Northrop/White Sands NM (NM), or the Kennedy Space Center (KSC).
The Time of Ignition (TIG) and Landing Times are presented, along with the lighting conditions at landing (ar = hh:mm after sunrise, bs = hh:mm before sunset) and the crossrange distance of the pre-burn orbit grountrack to the landing site (in NM).
Deorbit Digitals
The Deorbit Digitals display gives the FDO a detailed look at the upcoming planned deorbit burn.
This display is extremely critical to the Entry FDO, since the deorbit burn sets up a “no-return” scenario for the Space Shuttle. Once the deorbit burn is executed, the Shuttle is committed to landing wherever the FDO has targeted it.
All of the planning and preparation must be exact, and the post-deorbit burn trajectory and entry simulation that defines it are scrutinized by the FDO, the TRAJ, and a host of other MPSR support personnel.
Entry Groundtracks
The Entry Groundtrack displays are some of the easiest-to-understand displays that the FDO uses, but are also some of the most difficult to explain!
The next three displays show the same entry trajectory at three different scales. This is a simulated entry to KSC using runway 33.
Entry Groundtrack – large
The first display shows the “large scale” groundtrack display of the entry trajectory as it approaches Florida.
The green line is the nominal entry trajectory computed by FDO. The yellow line is where onboard guidance thinks it is, and the red line is where ground based tracking shows the orbiter to be.
As you can see, there were a few discrepancies in the state vectors that this simulation provided for the Entry FDO to work.
Entry Groundtrack – intermediate
The second display shows an intermediate scale as the Shuttle approaches KSC.
The ground features are, again, outlined in blue. If you’re not familiar with the terrain at KSC, this might appear confusing, but if you look at a KSC-area map, it’ll make more sense.
The Heading Alignment Cone (HAC) is represented by the twin circles prior to aligning for final approach to the runway. The Shuttle is able to make the final alignment turn to either the left or the right, depending on the runway and the groundtrack approach direction. In this case, it’s an “Overhead Right” turn.
Entry Groundtrack – HAC
The third display shows that the state vector issues we saw on the first display have all been (thankfully) resolved, and the trajectory plot points were all well in-line throughout the HAC intercept and Approach-and-Landing (A/L) phases.
This screenshot was taken after the Shuttle had (simulated) landing at KSC33.
