README web version of /home/usg/OPS/MTS/readme_xml/readme_81091304

Principal Investigator Email Address

• boekel@mpia.de

Estimated Total Execution Time (hours, including overheads)

• 2.0

General Description

• This program aims to further constrain the structure of the \"transitional\"
   young stellar
  object TW Hya. The disk of TW Hya has an \"inner hole\", a central region that is
   largely
  (but not entirely) devoid of dust (and gas?). Recently, a giant planet was discovered
  within this gap in this ~10 Myr old system.
  
  The MIDI observations probe the boundary between the cleared \"inner\" disk region
   
  (about <1 AU) and the still optically thick \"outer\" disk region (>1 AU).
  
  
  !!!! THESE OBSERVATIONS ARE CHALLENGING, BUT FEASIBLE !!!!
  
  Due to low (correlated and total) fluxes of TW Hya, these observations are pushing
  the limits of what MIDI can do. Yet, the object was already measured with MIDI during
  GTO under good weather conditions, and we obtained good results which have recently
  been published. Thus, given the right conditions (meaning: clear (no cirrus) and
   a
  relatively long coherence time), these observations should not be a \"mission-impossible\".
  
  There was some discussion between us and the Paranal Staff (via Christian Hummel)
   about
  whether we should do these observations in visitor or service mode. The Paranal
   staff
  decided the chances for succes were better in service mode (as we originally requested),
  thus the decision was made for service mode observations.
  
  Besides the optical finding charts, we have also attached actual MIDI acquisition
  images, to give you the best possible idea of what to expect.
  
  Good luck!!!

Waiver Requests

• No Waiver Request was submitted

Critical Observing Condition Constraints

• No cirrus
  relatively long coherence time (very low correlated fluxes!)

Time-Critical Aspects

• Baseline have been chosen such as to best complement existing measurements,
  and to optimally separate the effects of radial and azimutal variations in
  the source brightness on the visibilities.
  
  Acceptable ranges in LST have been indicated in the  OBs.
  
  
  A note on the timing of the Calibration observations:
  the calibrator star was chosen such that it \"trails\" TW Hya somewhat.
  Thus, the optimum observing time is always *after* the science observation.
  This is also the most practical solution, since then we only have to do
  the calibrator observation when we know the science observation was
  successful, and the two observations will be more closely spaced in time
  (the calibrator will work in 1 go since it's bright and easy, the science
  target may require a somewhat more time consuming acquisition).

Special Execution Requirements

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Special Calibration Information

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ToO Information

• ---(Empty)---

ToO Activators List

• ---(Empty)---

Is this a Pre-imaging run ?

• false

Pre-imaging Requirements

• ---(Empty)---

Source(s) of Pre-imaging

• ---(Empty)---

Pre-imaging sources not listed above

• ---(Empty)---

Do all your OBs comply with the instrument-specific requirements listed
 on the instrument-specific Phase 2 web page ?

• YES

If this is a pre-imaging run, did you select PRE-IMAGING for the Observing
 Category for each Observing Template ?

• N/A

Do all your finding charts comply with both the general and instrument-specific
 Phase 2 Web Pages ?

• YES

If you submitted OBs for standard stars, did you specify the magnitude
 and spectral type of all standard stars in the OBs ?

• YES

Have you included OBs for any calibrations that you need but which are
 not part of the Calibration Plan ?

• YES

If you are observing Moving Targets, have you attached suitable ephemeris
 files to your OBs?

• N/A

If you have preferences which OBs should be executed first, did you make
 use of the User Priority field in the OBs ?

• N/A

If this is a run that requires coordinated observations with other facilities,
 did you give proper instructions in the Time-Critical Aspects Section ?

• N/A

Did you indicate for each science star OB the corresponding calibrator
 star OB (and vice versa) in the 'Instrument Comments' field ?

• YES

Did you check that your chosen calibrator is bright enough for the instrument
 mode used ?

• YES

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 ?

• N/A

Did you verify that your coordinates are as accurate as possible (2Mass
 coordinates recommended) and that they include proper motions if available ?

• YES

Did you specify the LST range of the calibrators such that they cover
 the range from 30 min before the start of the LST range of the science target to
 30 min after the end of the LST range of the science target ?

• N/A