LCS: prelimiary 271b schedule

[Leonid Petrov <Leonid.Petrov@xxxxxxxxxxx>]

Dear colleagues,

  Time slot for the next LCS experiment, 271b, was alloted:
[2008.11.28_09:00:00, 2008.11.29_09:00:00].

  I prepared a preliminary schedule:

http://vlbi.gsfc.nasa.gov/lcs/v271b/v271b.vex
http://vlbi.gsfc.nasa.gov/lcs/v271b/v271b.plan
http://vlbi.gsfc.nasa.gov/lcs/v271b/v271b.stat
http://vlbi.gsfc.nasa.gov/lcs/v271b/v271b.skd
http://vlbi.gsfc.nasa.gov/lcs/v271b/v271b.skf

   The difference with respect to the previous schedules:

1) The newest version of AT20G catalogue, 2008.10.30 was used as 
   the basis catalogue for candidate selection.

2) The number of scans per source was increased from 3 to 4.
   This change is made for two reasons: first, to reduce the probability
   of false group delay ambiguity resolution, second to improve the 
   accuracy of positions.

3) The minimum time between scans was set to 3 hours.

4) The maximum declination was raised to -45 deg. Our VLBA proposal 
   for observing in the declination range of [-50, -30] deg was rejected 
   for the second time on the grounds that "LBA can do this job better". :-(

Summary of the schedule:

Tag_usage:     6 sources are observed in  1 scans
Tag_usage:     2 sources are observed in  2 scans
Tag_usage:    25 sources are observed in  3 scans
Tag_usage:    66 sources are observed in  4 scans

Total on source time:  13.68 hours, efficiency: 0.570
On target source time: 11.63 hours, efficiency: 0.485

# scans:  431    # observations:   6465

So, in total, 91 sources will be observed in 3 or 4 scans.

----

Correlation of v271a is under way. I peeked at results of the preliminary
correlation (4 stations only). They look promising:

 Correlated:                                            1564 
 Number of potentially recoverable observations:        1222            
 Number of potentially good observations with QC 5-9:   1223            
 Number of used observations:                           1159  ( 94.84%) 

 Quick look at v271a
  
 127 scheduled
 126 observed
 118 detected

Detection rate is 93%. Resolving ambiguities was a bigger problem for this
experiment, but it went through. It is difficult to tell anything about
astrometric quality, since two few baselines were processed.

  But resolving group delay ambiguities went smoothly only at ATCA-104/MOPRA
baseline. I resolved ambiguities for 97% sources, but for some of the 
sources ambiguity resolution is not reliable. I expect, analysis of all the 
data will reduce or eliminate the problem, but as a precaution I think it
is worth to increase the number of scans per source.

We need to finalize the schedule by 2008.11.17. Comments? Ideas? Suggestions?

Sincerely,
Leonid Petrov
09-NOV-2008 22:41:25