Gene and Danny:

Here is the time line for the MEX BSR on day 170 (local time Saturday 08:10
to 14:10) at DSS 63.  The ground track for this one is exciting, but the
experiment itself will look familiar.

The surface echo starts well above the carrier and drifts slowly upward for
about 45 minutes.  Then it reverses direction and eventually hurtles into the
carrier at ingress occultation.  Whether we see the final events is not clear
from the DSN Keyword File, but I have done the time line assuming we end with
at least an X-Band occultation.

For the first 26 minutes after BOT there is no signal.  S- and X-Band come
on, and there is 15 minutes of low-priority X-Band telemetry while the S-Band
transmitter warms up.  We have the usual spacecraft calibration and slew to
Mars with surface observations beginning at 18:28 UT.

At this point, the reflecting region is at the base of Pavonis Mons (2S,
115W), the central Tharsis volcano.  Incidence angle is 40 deg, so most of
the echo will be LCP; but this is expected to be a poorly reflecting region,
so you may not see much in either polarization.  Over the next 30 minutes,
the specular point drifts slowly southwest until it is climbing over Arsia
Mons, the southern volcano.  There may be a time (18:54 UT) when we are
getting reflections from the summit caldera (10S, 120W), though my
calculations indicate we will not score a direct hit.  After leaving Arsia
Mons, the reflecting region wanders further south; at 19:32 we are at (32S,
120W) and incidence angle is 60 deg - RCP and LCP should be about equal.
Incidence angle continues to increase (more RCP), the spacecraft drops toward
periapsis, and we have occultation at about 20:02 (51S, 53W).

The DSN keyword File indicates that the spacecraft antenna returns to Earth
point about 19:51 and that X-Band telemetry comes on and the S-Band
transmitter goes off at 20:01.  I think we just leave things running for BSR
and see what happens.  There is 65 minutes to do the second MINICAL and the
post-cal, which should be plenty.  If it looks too tight, feel free to use 2-
minute time steps for MINICAL #2 and/or the post-cal.

For playback, I recommend the following for the 25 kHz data (no segment
longer than 88 minutes):

       Pre-cal
       Track until start of 100 kHz data
       Surface observations until 19:15
       Remaining surface/occultation observations (to end of 100 kHz data)
       Remaining track (e.g., MINICAL #2) and post-cal

For 100 kHz playback three 21 minute segments, a 20 minute segment, and a 13
minute segment would be best.  This puts the confirmed surface observations
into the first four files, with the iffy surface data and occultation in the
short file at the end.

I expect to be at Donner Summit for this experiment.  Try the cell phone
(650-380-0675) first; the landline (530-426-3536) is backup.

Thanks,
Dick


2010/170 (UTC)
- - - - - - -

15:10  Begin Pre-cal at DSS 63
       FGAIN = 60 dB (all channels, except X-RCP)
               65 dB X-RCP
       FRO_X = 0; FRO_S = 0 (all SCHAN)
       Start 4-channel 25 kHz recordings after Step 5 (new NOP)
       Stop 25 kHz recording after Step 20 (new NOP)

17:10  Begin track (no signals at either S- or X-Band)

17:36  S-Band AOS
       X-Band AOS (telemetry ON; ignore it)

17:51  Resume 25 kHz recording

       X-Band telemetry OFF

17:55  Advise DSS 63 of switch to planetary coordinates at 18:05
       Advise DSS 63 of start of MINICAL #1 at 18:10

18:01  Begin SLEW #1

18:05  DSS 63 switch to planetary coordinates

18:06  FRO_X = +45000 Hz (SCHAN 3)
       FRO_S =  +8000 Hz (SCHAN 3)

       FRO_X = +28000 Hz (SCHAN 4)

18:10  Begin MINICAL #1

18:25  End of MINICAL #1 (end of step 5)

18:28  End SLEW #1

       Begin 100 kHz recording (SCHAN 4)

18:38  FRO_X = +55000 Hz (SCHAN 3)

19:17  Maximum upward drift of echoes

19:39  FRO_X = +45000 Hz (SCHAN 3)

19:45  FRO_X = +36000 Hz (SCHAN 3)

19:49  FRO_X = +28000 Hz (SCHAN 3)

19:53  FRO_X = +18000 Hz (SCHAN 3)
       FRO_S =      0 Hz (SCHAN 3)

19:56  FRO_X =  +9000 Hz (SCHAN 3)

19:59  FRO_X =      0 Hz (SCHAN 3)

20:00  Advise DSS 63 that MINICAL #2 begins at 20:07
       Advise DSS 63 that EOT is delayed from 20:10 to 20:22

20:02  Ingress occultation

20:04  End 100 kHz recording (SCHAN 4)

20:07  Begin MINICAL #2

20:22  End MINICAL #2 (end of step 5)

       Delayed end of track (scheduled EOT 16:15)

       Go to zenith

       Begin post-cal when ready

21:10  End post-cal (or earlier, if post-cal complete)

       End 25 kHz recordings

       End of Activity