Title  A TOO observation of an Oort cloud comet 
Pi     D. Bockelee-Morvan
Time   168 hrs

1. Name of program and authors 
   A TOO observation of an Oort cloud comet 
   Authors: D. Bockelee-Morvan, N. Biver, J. Crovisier, J. Boissier 
 
2. One short paragraph with science goal(s) 
   This is a target-of-opportunity program for observing a bright  
   new comet with a water production rate of 1.E29 mol/s. Statistically,  
   such a comet appears once per year. With ALMA it will be possible to 
   determine the relative abundances of a number of species in its coma, 
   for comparison with other Oort cloud comets and Jupiter family comets. 
   Minor species identified in comet Hale-Bopp should be detected. In 
   addition, several isotopic species will be observed (e.g. HDO, DCN, 
   H13CN, HC15N, CS C- and S isotopes), whose abundances are key indicators 
   of the origin of cometary material. The observations are very similar to 
   the Earth-grazing comet example. 
 
3. Number of sources  
   Typically one per year 
    
4. Coordinates: 
 
4.1. Rough RA and DEC  
 
4.2. Moving target: yes 
 
4.3. Time critical: yes 
 
4.4. Scheduling constraints:  
 
5. Spatial scales: 
 
5.1. Angular resolution (arcsec): 
       
     -Compact configuration (1-2 arcsec)for lines 
     -Typically 5 km baselines for nucleus continuum observations 
      (for nucleus/coma contrast > 10)  
     - For weak lines, auto-correlation measurements may be more sensitive     
 
5.2. Range of spatial scales/FOV (arcsec): 
  
5.3. Required pointing accuracy: (arcsec) 
     0.5" 
 
6. Observational setup 
 
6.1. Single dish total power data: beneficial 
 
     Observing modes for single dish total power:  
     frequency switch 
 
6.2. Stand-alone ACA: no 
 
6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas:  
     beneficial 
 
6.4. Subarrays of 12m baseline-ALMA antennas: no 
 
 
7. Frequencies: 
 
7.1. Receiver band: Band 3, 4, 5, 6, 7, 8  
 
7.2. Lines and Frequencies (GHz):  
      
     multi-line observations  
      
 
7.3. Spectral resolution (km/s): < 0.1 km/s 
 
7.4. Bandwidth or spectral coverage (km/s or GHz): 
     8 GHz in continuum mode 
     depends upon frequency setup in spectroscopic range  
     (e.g. large coverage for covering many lines at the same time) 
 
8. Continuum flux density:  
 
8.1. Typical value (Jy) 
     nucleus : ~ 2 mJy for 10 km size comet nucleus at 1 AU from Earth 
 
8.2. Required continuum rms (Jy or K):  
 
8.3. Dynamic range within image: 
 
8.4. Calibration requirements: absolute      ( 10% ) 
                               repeatability ( 10% ) 
                               relative      ( 10% ) 
 
9. Line intensity 
 
9.1. Typical value (K or Jy): 
     depends upon line : 0.1 to 12 K km/s in 2 km/s velocity range for 
     compact comfiguration.  
      
9.2. Required rms per channel (K or Jy): depends upon line 
 
9.3. Spectral dynamic range: 
 
9.4. Calibration requirements: absolute      (10%) 
                               repeatability (10%) 
                               relative      (10%) 
 
 
10. Polarization: no  
 
 
11. Integration time for each observing mode/receiver setting (hr): 
    several frequency setup, with different integration times 
 
12. Total integration time for program (hr): 168h 
 
 
13. Comments on observing strategy :  
     Target of Opportunity 
     Line mapping requires ALMA to be in compact configuration. Nucleus 
     investigation requires more extended configurations. 
     So the observing strategy will depend upon Alma configuration at time 
     of comet perihelion. 
      
 
 
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Review v2.0:
 
Review of 4.3.1-4.3.9

These projects have all been updated to v2.0 and a new, timely project
on D/H has been added.

One issue that all projects share is their use of the ACA in
crosscorrelation with the ALMA-12m antennas. Are the common baselines
really essential, or would *simultaneous* (but standalone) ACA
observations also work? This might be much easier on the system
(slewing times; correlator; ...). Fully standalone (and therefore
separate in time) ACA observations for comets obviously make little
sense (...although, one could think of cases where some large-scale
monitoring could be useful). 

Comment: the integration times do not seem to be worked out in much
detail, although the total times listed seem of the correct
magnitude. This may be the best that is currently feasible. (cf. v1.1
where more detailed estimates are given).