README web version of /home/usg/OPS/MTS/readme_xml/readme_75020100

Principal Investigator Email Address

• marcello.fulchignoni@obspm.fr

Estimated Total Execution Time (hours, including overheads)

• 8h

General Description

• Science goals: The program asks for high S/N imaging polarimetry of
  asteroid 2867 Steins, target of the Rosetta mission, at different phase angle aspects
  in R and V filters. The goal is to measure the degree of polarization with change
   of the phase angle of the object (between 29 and ~9.5 deg) at 8 epochs during June-Sept
   2005. For this reason we ask for 8 independent observations of about 1 hour each
   in this period.
  tThe results will allow to compute important parameters of the asteroid polarization
   curve needed to determine the asteroid albedo and to give some constraint on its
   surface composition.
  The evaluation of the albedo is fundamental to derive the real size of the asteroid
   and so to optimize the Rosetta fly-by operations.

Waiver Requests

• No Waiver Request was submitted

Critical Observing Condition Constraints

• Asteroid polarization values are of the order of few percent, so we need
   high signal to noise measurements to minimize the errors. To avoid the moon influence,
   we require lunar phase < 0.7 and an asteroid--moon distance greater that 30 deg.
  We need high S/N (~1000) measurements for our purpose, so we set the exposure times
   in order
  to have more than about 40000 counts with "mean" seeing conditions (0.7-1"). However,
   in case of very good seeing conditions, please check the signal and eventually lower
   the exposure time in order to avoid possible saturation.
  According to the p2pp instructions for moving targets, no finding charts are required
   for blind presets. Field identification by a on-line DSS image is enough, the asteroid
   is the additional object near  the center of the DSS star field

Time-Critical Aspects

• We need to obtain polarization measurements of the asteroid at different
   phase angles (29-9.5 deg) during the June -Sept. 05 period. For this reason for
   each OB we put an observing window of 5-14 days, in different period during June-September
   2005, in order to cover different phase angle aspects of the asteroid and built
   the its polarization curve as a function of the phase angle. For each OB we put
   the time interval contraint.

Special Execution Requirements

• Please note that our target is a moving object so ephemeris and differential
   tracking must be adjusted at the time of observation according to the ephemeris
   file provided.
  Our OBs consist of a 8 couple of target +nonpolarized std star. In fact, do to the
   small polarization asteroid values, we need high accuracy both in the target signal
   (so high S/N ratio)  and in the instrumental polarization evaluation, and the asteroid
   observation must preferentially be accompanished by non polarized std observation.
  We set the name of the OB  in the following way:
  MOV_name_period (for instance: MOV_2867Steins_3jun-18jun), where MOV=  moving target
   (or STD for standard star),name = name of the target, period = desirable execution
   periods of OB.
  The 8 hours allocated must that be splitted in 8 independent observations each with
   the target and non pol. std. acquistition

Special Calibration Information

• Polarized standards: Calibration through polarimetric standard stars
  according to FORS1 calibration plan. No special OBs are provided and
  standard VLT OBs for this task are fine.
  Unpolarized standards: 1 OBs for each observing window to observe unpolarized standards
   is
  provided. Please, perform the std OB  close to the object observation
  We also need sky flat fiels in R and V filter, polarimetric mode, durinf twiligth

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 ?

• N/A

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?

• YES

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

• YES

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

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 ?

• YES