README web version of /home/usg/OPS/MTS/readme_xml/readme_79506202
Principal Investigator Email Address
Estimated Total Execution Time (hours, including overheads)
General Description
The goal is to recover comet 85P/Boethin, the target of the DIXI
mission. This is a mission critical observation; we must find the
comet before Oct 15. We have a candidate seen in CFHT data from August;
the estimated magnitude is V=27.3+/-0.5. If this is the nucleus, it is
small and probably irregularly shpaed, and we do not have any
information on its rotation period or pole direction. The observations
are planned assuming the August data could have caught the comet at its
maximum brightness, thus we are planning for a detection at mag 27.8.
We will do this be combining data from UT1, UT, and UT3, along with data
from the SOAR4m, CTIO4m, Gemini S 8m, and possibly Magellan 6.5m. Because
we have a very limited period of visibility, the S/N calculations assume
less than ideal conditions (seeing 1.3-1.5", avg airmass of 1.6, but with
clear, dark skies).
The observations are simple: image as deep as possible (1 hr total exposure
per telescope) through a series of shorter exposures on each of 2 nights on
each of 3 VLT telescopes.
Waiver Requests
Critical Observing Condition Constraints
Time-Critical Aspects
The comet is visible from the end of ATwi for ~1 hour per night
before the airmass gets too high. The first night
for the observing window is UT Sep 29; this is the first night
when the moon is not up at the time of the comet observation - we
need dark sky. The visibility window rapidly decreases by Oct 9.
Programmatically all the data must be reduced and we must have an
answer for NASA before 10/15.
The specific DDT request was written as 30 min exposure on target per
night x 2 nts for each of UT1, UT2, and UT3. I was ~new to the P2PP
process and thus could only estimate the overheads. I wrote explicitly
in the proposal that this was likely to be 10-15 min per night per
telescope. Thus, the request was to take 1.33-1.5 hr per telescope.
The ESO LaTeX form produced 1.3hr per telescope. Now that we have
used P2PP to estimate the execute time, the actuals are:
FORS1 1.38 hr 83.2 min
FORS2 1.39 hr 83.8 min
VIMOS 1.67 hr 100.5 min
This is within the envelope of what was explicitly written into the
proposal for the total time, but violates the page 1 proposal
summary. Will this be a problem? As this must be done at the start
of the night, can some of the acquisition set up be done at the end of
Astronomical Twilight?
Special Execution Requirements
1. The observations must be guided at non-sidereal rates (included in
the ephemeris files.
2. We will use the standard calibration plan, including photometric
standards
3. The target will be observed with 30 min total integration
time per night on each of 2 nights on each of the 3 telescopes
4. The nights do not need to be contiguous. It will greatly help
the image processing for background subtraction if the data are
not obtained on the same night for the different telescopes.
(i.e. if all three telescopes observe on the same night we
cannot do as good a static sky removal as if the data are
spread over several nights)
5. Each OB contains 10 shorter exposures dithered to remove the chip
gaps for FORS1 and FORS2, and 8 shorter exposures for VIMOS
(to reduce overhead)
6. Each OB should be repeated on a second night. Positions are to be
updated each night from the ephemeris file.
Finder Charts
P2PP has a limitation of loading only 4 finder charts per OB. We have
finders made from Sep28 through Oct10 UT. Four finders each have been
attached to the OBs:
FORS1 (Oct 5, 6, 7, 8)
FORS2 (Oct 1, 2, 3, 4)
VIMOS (Sep 28, 29, 30, Oct 9)
Comments about the VIMOS offset
We put in an acquisition offset of 4 arcmin E and 5 arcmin S for the pointing
for the initial VIMOS observation. With the instrument rotator at PA=0,
this should place the candidate in the center of Quadrant 2. We prefer
to put the object in Q2 - and have a large amount of the FOV to the east.
The candidate is about 2.5 arcmin W of the nominal ephemeris, and this
will allow us to also image the ephemeris position as well as the error
ellipse to the East of the nominal position.
Comments about the FORS1 and FORS2 pointing
Since the default (0,0) coordinates are on the top chip centered in X and
toward the lower part of the top chip, we do not need a large acquisition
offset as we did for the VIMOS detector. Instead we start with the
dithering pattern and a small offset.
Special Calibration Information
ToO Information
ToO Activators List
Is this a Pre-imaging run ?
Pre-imaging Requirements
Do all your OBs comply with the instrument-specific requirements listed
on the instrument-specific Phase 2 web page ?
If this is a pre-imaging run, did you select PRE-IMAGING for the Observing
Category for each Observing Template ?
Do all your finding charts comply with both the general and instrument-specific
Phase 2 Web Pages ?
If you submitted OBs for standard stars, did you specify the magnitude
and spectral type of all standard stars in the OBs ?
Have you included OBs for any calibrations that you need but which are
not part of the Calibration Plan ?
If you are observing Moving Targets, have you attached suitable ephemeris
files to your OBs?
If you have preferences which OBs should be executed first, did you make
use of the User Priority field in the OBs ?
If this is a run that requires coordinated observations with other facilities,
did you give proper instructions in the Time-Critical Aspects Section ?
Did you specify suitable guide stars for all your OBs using Guidecam
?
Did you check that the chosen guide stars are suitable for all the offset
positions and that they do not produce unacceptable vignetting of the field of view
?
Last creation of page: Tue Oct 6 15:40:20 2009
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