README web version of /home/usg/OPS/MTS/readme_xml/readme_77022604
Principal Investigator Email Address
Estimated Total Execution Time (hours, including overheads)
General Description
This propsal concerns circumstellar disks around young intermediate mass
stars.
It aims to verify of disprove hypothesis about
1. the spatial structure of such disks,
2. the dust properties in the disks, especially the spatial distribution of different
dust species.
Due to the nature of the objects and the technique, it is important to measure in
a specific
LST interval (for this sub-run E, constraints are especially stringent). Below there
is some
more information fyi, (after the note on the finding charts), but this is not needed
for
proper execution of the OBs
A note on the finding charts:
The science OBs have 'normal' finding charts attached, but additionally contain
UV plots
displaying positions in the UV plane corresponding to the best times for the measurement
("optimum hour angle"), and the tolerances (uv points at minimum and maximum of
the hour
angle range).
Optional reading:
1. and 2. concern the *radial* behaviour, i.e. how things change with distance to
the central star.
Since visibility data is still very scarce and getting good 2D coverage of the UV
plane is
too time-costly, we have to adapt a strategy that circumvents that problem. We have
chosen
to measure visibilities at baselines of different length, but approximately the
same position
angle on the sky. We measure at 3-4 baselines for each object, in order to sample
the predicted
visibility behaviour (see ascii art below, and the proposal for more details). The
behaviour
of visibility curve is thus sampled, even if the disk inclination/orientation are
unknown
(observing an inclined disk yields qualitatively the same curve as sketched below,
but
"expanded" in the baseline direction if one looks along the minor axis of the system.
1 |_
| \
| \
V | \
| \_________
| \____
| \__
| | | | | \_ __---__
0 |________________________\/_______\__
0 200
Baseline
A sketch of a predicted visibility curve (see proposal for more details). The
baselines at which we sample it, are indicated by the | symbols.
Waiver Requests
Critical Observing Condition Constraints
Time-Critical Aspects
In the attached UV plots we have indicated the uv points corresponding
to the "best" hour angles,
the minimun and maximum hour angles. On the U2-U4 baseline the tolerances are small:
36 and 39 minutes
(in the other subruns, tolerances are 1 hour or more). These thus are the "critical"
points of
the programme. We realize this is difficult to plan, but still stress the importance
of getting the
hour angles right, and ask you to use the flexibility that only service mode observations
can give.
(for example, you can observe calibrator-science or science-calibrator, just whichever
way the hour
angle for the science target fits best. Maybe if today we can't get the source in
the required time
slot because the preceeding observations took longer than planned, try the critical
observation tomorrow.
We realize this is hassle and apologize.
Many thanks for your cooperation!
Roy van Boekel
Special Execution Requirements
Due to the geometry of the whole system, the observatoins on this baseline
are
especially sensitive to timing (more so than the observations in the other
sub-runs in this program).
The science case is built on having accurate visibilities (within 2 or maybe 3 percent).
This calls for sci-phot mode. We *easily* found and tracked fringes on 2 out of
the 3
sources in this programme on UT2-UT3, under *bad* circumstances (+2 arcsec seeing,
MCAO
loops opening and closing all the time, big mess). Therefore, it should under "normal"
(i.e. not exceptionally good, but not too bad either) circumstances not be a problem
to perform these measurements in sci-phot mode. Due to the nature of the science
case,
it is *NOT* helpful to switch to high-sens in case fringes cannot be found. But
as said,
the already measured fringes tell us that when fringes can't be found, likely the
conditions
are bad or the system's not functioning as well as it could/should!
Probably best to start with the shortest baselines, and work your way through towards
the longest!
Special Calibration Information
hd_139997, Flux 20.8 Jy @ 10 micron, spectral type K5III
hd_146003, Flux 20.2 Jy @ 10 micron, spectral type M2III
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 ?
Did you indicate for each science star OB the corresponding calibrator
star OB (and vice versa) in the 'Instrument Comments' field ?
Did you check that your chosen calibrator is bright enough for the instrument
mode used ?
If you use calibrator stars which are not in the CalVin database, did
you specify their characteristics in the README file and in the OBs ?
Last creation of page: Tue Oct 6 15:40:12 2009
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