README web version of /home/usg/OPS/MTS/readme_xml/readme_79506200
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. We have a candidate seen in CFHT data obtained in August; the
estimated magnitude is V=27.3+/-0.5. If this is the nucleus, it is
small and probably irregularly shaped, and we do not have any
information on its rotation period / pole direction. The observations
are planned assuming the Aug data could have caught the comet at max
brightness, thus we are aiming for a detection at mag 27.8. We will do
this by combining data from UT1, UT2, and UT3, along with data from the
SOAR4m, CTIO4m, Gemini 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", airmass of 1.6, but with
clear, dark skies).
The observations are simple: image as deep as possible through a
series of shorter dithered 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 end of astronomical twilight for ~ 1 hour per
night before 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 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 thus 1.33-1.50 hr per telescope. The
The ESO latex form produced 1.3 hr 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 Total = 4.44 hr
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. Observations must be guided at nonsidereal rates (included in the
ephemeris file).
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 have to be contiguous and all the telescopes
do not need to observe on the same night. It helps with the
median static sky removal to have observations on different nights.
5. Each OB containes 10 shorter exposures dithered to remove the chip gaps
for FORS1 and FORS2, and 8 shorter exposures for VIMOS
(to reduce the overhead).
6. Each OB should be twice - once per 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 Sep 28 through Oct 10 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)
This was the only way to get all 12 dates into the system.
Comments about VIMOS offset
We put in an acquisiont 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 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
Source(s) of Pre-imaging
Pre-imaging sources not listed above
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 ?
If you have prepared your finding charts with tools other than FIMS,
do they comply with the specifications on the FORS1 Phase 2 web page ?
Last creation of page: Tue Oct 6 15:40:20 2009
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