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SXT Pointings and Terminator Pointings

Image name: Terminator_Planning_Info.png (click image to enlarge)
Image size: 10.4150 KB (980x980)
Date submitted: 08-Mar-1995


This figure shows all of the FFI pointings recorded in the observing log
since November 1992 up to February 1995.  Also shown as gray + symbols
are the locations of terminator pointings up until Feb 1995 from the SFT
records.  It is obvious that we have many FFI data for which there are
no appropriate terminator straylight correction images. 

The 7 locations I chose for additional termiantor observations on
15-Feb-95 are shown on the figure.  These choices were fairly arbitrary.
These pointings were turned into OG commands at that time and uploaded
to Yohkoh and are available for use.  They are

     Case    EW-direction    NS-direction    OG number   OG title
		(arcmin)	(arcmin)     (decimal)
       0        W 19.729        S 1.094         33      S/C W19S01
       1        W 17.374        N 0.142         34      S/C W17N00
       2        W  9.780        S 0.761         35      S/C W10S01
       3        W  3.532        N 0.094         36      S/C W04N00
       4        W  3.484        N 1.521         85      S/C W03N02
       5        E  3.628        N 0.094         86      S/C E04N00
       6        E 18.047        N 0.475         87      S/C E18N00

However, these Yohkoh pointings are not correct in perpetuity because of
the drift between S/C commanded (CMD) and SXT attitude (ATT) positions. 
This drift is illustrated in the SHOW_PIX calibration file
Attitude_vs_Temperature.  Thus, to actually achieve the correct pointing
for needed terminator images the offpoint OGs must be determined as
near as possible to the time of the observation.

With Hugh Hudson's help I have prepared routines to simplify this process.
They presently reside in /1p/acton/terminator and the relevant files are

-rw-r--r--   1 acton    people   1922144 Feb 15 22:28 offpnt_imgs.sav
-rw-r--r--   1 acton    people      2156 Feb 15 22:53 offpoint_15Feb.txt
-rw-r--r--   1 acton    people      2831 Mar  9 04:22
-rw-r--r--   1 acton    people      1954 Feb 15 20:39
-rw-r--r--   1 acton    people      7024 Mar  3 17:16 sft_points.3.3.sav
-rw-r--r--   1 acton    people   4532128 Feb 22 10:23 sxtf_points.2.17.sav is a low_level program which converts offpoint Euler angles
to block commands in hex. is a program to get the
offpoints and block commands by cliking on a plot like this figure.  The
IDL save file offpnt_imgs.sav has this figure and the same one but without
the 7 chosen cases so you can use it with if you don't want
to prepare your own.  offpoint_15Feb.txt is an example of data prepared
with these programs for use by the tobans to generate OG commands. 

The files sft_points.3.3.sav and sxtf_points.2.17.sav have structures
prepared by Mark Weber giving the pointings in FR coordinates, the image
times and the filters used of all of, respectively, the sft terminator
images throughout the mission and all of the FFI images since Nov '92. 
These data were used in preparing the figure given here and can serve as
the basis for future terminator planning.

						L. Acton  8-Mar-95

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