Title  Characterization of the Jupiter-family comet population 
Pi     D. Bockelee-Morva
Time   200 hrs

1. Name of program and authors 
   Characterization of the Jupiter-family comet population  
   Authors: D. Bockelee-Morvan, N. Biver, J. Crovisier, J. Boissier 
 
2. One short paragraph with science goal(s) 
   About 30 comets have been observed by millimetre/submillimetre  
   spectroscopy.  A large diversity is observed in the relative abundances of  
   parent molecules, such as HCN, CO, H2S, H2CO ... etc. However, only a few  
   Jupiter-family comets could have been investigated because of their low  
   activity, while they may present distinct composition with respect to  
   Oort cloud comets. The sensitivity of ALMA opens a new window for 
   establishing their composition.  We propose to observe a few Jupiter-family  
   comets (other than Earth-grazers) spectroscopically.  We also propose to 
   observe at least a few of them for thermal emission from the nucleus, at  
   least Comet 81P/Wild 2 (target of NASA Stardust mission) and 10P/Tempel 2. 
 
3. Number of sources  
  one every two years 
    
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 : 0.02 mJy for 1 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 
     from 0.02 to 3 K km/s (2 km/s line widths) in compact configuration 
 
9.2. Required rms per channel (K or Jy): depends upon line, S/N > 5 
 
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): 200 h 
 
 
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. 
     Line monitoring : can be done in single-dish mode  
 
 
--------------------------------------------------
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).