Title  Search for extrasolar planets via astrometry of nearby stars
Pi     B. Butler
Time   144 hrs

1. Title: Search for extrasolar planets via astrometry of nearby stars
   Authors: B. Butler  
   program 4.4.3

2. Science goal:

   The orbit of any planet around its central star causes that
   star to undergo a reflexive circular motion around the star-planet 
   barycenter.  By taking advantage of the incredibly high resolution 
   of ALMA in its widest configuration, we may be able to detect this 
   motion.  Taking the stellar catalogs of Gliese & Jahreiss (1988) 
   and Hipparcos (Perryman et al. 1997), and computing how many of 
   these might have detectable wobble gives:
    companion mass    # G&J    # Hipp
      5*jovian         200      800
        jovian         120      180
      neptunian         30        0
   Details are in Butler & Wootten (2000).  Realistically, we might
   expect to monitor some few hundred of these, perhaps up to 1000,
   notably the solar-type ones in the G&J catalog (of which there are 
   130 total).  Each observation takes about 1 minute, so with overhead 
   this might be 1 day total for each set of observations (for 1000 stars), 
   which would be spread over several days to get the required sky
   coverage.  We will require at least 3 different epochs, and likely 
   more - a reasonable estimate might be one set of observations per 6 
   months, meaning 6 total sets of observations in 3 years.

3. number of sources: 100 - 1000

4. Coordinates:

 4.1. all over the ALMA sky

 4.2. Moving target: no

 4.3. Time critical: no

5.  Spatial scales:

  5.1. Angular resolution: 0.01"

  5.2. Range of spatial scales/FOV:  small

  5.3  Positional accuracy: 0.1 milli-arcsecond

6.  Observational Setup

  6.1. Single dish total power data: no

  6.2. Stand-alone ACA: no

  6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: no

  6.4. Subarrays of 12m baseline-ALMA antennas: no

7. Frequencies:

  7.1. Receiver band: 345 GHz

  7.2. Line: N/A

  7.3. Spectral resolution (km/s):  N/A

  7.4. Spectral coverage (km/s or GHz): N/A


8. Continuum flux density:

  8.1. Typical value:   0.1 - 10 mJy

  8.2. Required continuum rms (Jy or K): 0.1 mJy

  8.3. Dynamic range within image: low

  8.3. Required continuum rms: 0.01 mJy

  8.4. Calibration requirements: absolute      N/A
                                 repeatability N/A
                                 relative      N/A

9. Line intensity:

  9.1. Typical value :     N/A

  9.2. Required rms per channel: N/A

  9.3. Spectral dynamic range:   N/A


10. Polarization: no

 10.1. Required Stokes parameters:  N/A

 10.2. Total polarized flux density (Jy):  N/A

 10.3. Required polarization rms and/or dynamic range:  N/A

 10.4. Polarization fidelity:  N/A

 10.5. Required calibration accuracy:  N/A


11. Integration time per setting: 24 hrs

12. Total integration time for program: 144 hr

13. Comments on observing strategy :

   These are moving, albeit relatively slowly, but it will have
   to be accounted for properly since this is astrometry.  The
   timing is not critical, except to separate the sessions by some
   period of roughly 6 months.


-----------------------------------------

Review Leonardo Testi: See program 4.4.2
--------------------------------------------------
Review v2.0:
 
Review of 4.4.1-4.4.3

No updated required w.r.t. DRSP 1.1. Integration times still formally
hold for 64 antennas, so either increase the total times by 30% or
reduce the sensitivity by 14%. Other, unknown factors in the
sensitivity and performance will be larger than this correction.

R.:  This program is not jeopardized by the reduction of the number
  of antennae. Target list can be adjusted. The key point of this
  astrometric programm is the performance of ALMA in the extended
  configuration to benefit of the highest angular resolution of the
  instrument.