Study 000508:

ACRONYM: coronal_rain_1as2pos

**** This is a two-position raster, so  ****
**** please run one instance of a short ****
**** 40" slot raster before and after.  ****

This study is designed to capture instances of coronal rain, both at the solar
limb, and on the disc. It consists of two positions of the 1" slit, separated
by 20", with 12s exposures at each. 1" is used so that velocities can be
determined. 

One position located at the footpoints of AR loops, the other one 20" above,
along the loops direction, so choose a pointing exactly between these. 

At both positions the slit should be roughly perpendicular to the loop axes.

Fill up the available time (approximately 1 hr) by repeating this raster as
required, after taking the slot context raster.

TARGET:           Active Region. 
EXPOSURE TIME:    12s
RASTER:           Scanning
SLIT:             1"
STEP SIZE:        20"
FOV:              20"x256"
RASTER DURATION:  25s
VOLUME:           2.53 MBits
RATE:		  53.4 kBits/s
COMPRESSION:      DPCM is default

Instruction to planners:
-----------------------

* Run slot context (PRY_slot_contextLITE) x1, before and afterwards.
* 1 hour of continuous observation between ~10 and ~12 UT (overlap of SAA-free
  period with best seeing at La Palma (8 - 12 UT))
* Run study, using raster repeats to fill the desired time.
  (For reference, 1 hr = 144 repeats, but check the Planning Tool)

Pointing:
---------

This study is intended for use in conjunction with observations at the SST
(La Palma) and, preferably, with IRIS.

** Consult with Patrick Antolin (see HOP 234 details). **

Default guidelines for target: 

If IRIS is observing a QS region then co-observation with IRIS is not
desirable: please look for an AR on limb.

1. If IRIS is observing AR at limb:
   1st position centred on AR but 10" above the limb (above the spicular
   region). 2nd position 10" below the limb (close to where the footpoints of
   the loops would be). In this case, the slit orientation will most likely
   be parallel to solar limb.

2. If IRIS if observing an AR on-disc AND IRIS is running a wave program: 
   1st position at coronal loop footpoints and the 2nd one 20 arcsec away
   from the first, crossing the loops (roughly perpendicular to their axes).

3. If IRIS is doing none of the above then look for AR on limb and follow
   guideline #1. 

Warning:
--------

1) ** ADD ** 10 seconds per raster repeat (short raster duration). This is to
   allow for rasters synchronization

2) High TM rate (53 Kbit/s)