QUOTE (jmknapp @ Aug 22 2008, 07:25 AM)
Curious as to what the HUD polar display is showing.
Polar chart shows:
(Dist)ance and direction to actual touchdown point in m and degrees (all azimuths are in degrees, N=0, E=90, S=180, W=270)
(Hspd) Horizontal speed and azimuth in m/s
(FPA) Flight path angle in degrees, 0 is horizontal, +90 is straight down
(Alt)itude in meters
(Vspd) Vertical speed in m/s
(Vrel) Total ground-relative speed in m/s
(Acc) Non-gravitational acceleration (what's felt by accelerometers) in m/s^2
The vectors in the polar chart show the vector to the actual touchdown point (green) and the vector of current horizontal speed (yellow) in a logarithmic manner. Inner ring is 1m and 0.1m/s, and each next outer ring is 10x as much. Similarly the bars under altitude and vspd are logarithmic.
This is all modeled after the VTOL instrument in the Orbiter sim.
The vector ball in the upper right has bars every 45deg in latitude and longitude. It's polar axis is the local vertical. The red bar is true North. It shows the X, Y, and Z lander frame relative to the current viewpoint (red,green,blue). The local drag frame is shown with only vector arrowheads. The cyan arrowhead (mostly covered by the red vector) is the relative velocity. Assuming no wind, Drag is exerted opposite this direction. The yellow arrowhead is the "vertical" lift vector, perpendicular to the relative velocity vector and in the local vertical plane containing the relative velocity vector. The magenta arrowhead is the "horizontal" lift vector, perpendicular to both of these and as a consequence always in the horizontal plane. The orange arrow is the direction of acceleration as felt by the accelerometers (excluding gravity) and therefore registers 1 Mars G when sitting at the surface.
Upper left is a clock in UTC, spacecraft event time.
All the sound effects, as well as the music, come from the EDL HUD video published by NASA before landing. I can't take credit there. I just tweaked things to match the actual timeline, and am not done yet.