Title  is Hale-Bopp still alive?
Pi     D. Bockelee-Morvan
Time   12 hrs

1. Name of program and authors 
   Is Hale-Bopp still alive? 
   Authors: D. Bockelee-Morvan, N. Biver, J. Crovisier, J. Boissier 
 
2. One short paragraph with science goal(s) 
   CO outgassing is controlling cometary gaseous activity at  
   large heliocentric distances. The CO J(2-1) line was detected in comet  
   C/1995 O1 (Hale-Bopp) up to 14 AU from the Sun using the SEST  
   telescope.  At the beginning of 2011, Hale-Bopp will be at 31 AU  
   from the Sun and Earth. With deep integration with ALMA, we may be  
   able to recover the CO 230 GHz line. The line area over 0.6 km/s is  
   expected to be 0.0006 K km/s (T main beam), for a CO production rate  
   of QCO=1.1E27 mol/s. This production rate is expected if QCO decreases 
   as the square of heliocentric distance (as observed between 1 and 14 AU). 
   But modelling of sublimation processes often predicts a much smaller 
   decrease as due to sublimation from deep layers inside the nucleus. 
 
3. Number of sources  
   1 
    
4. Coordinates: 
 
4.1. Rough RA and DEC  
     RA = 0 DEC = -85      
 
4.2. Moving target: yes 
 
4.3. Time critical: no, but we cannot wait years ...  
 
4.4. Scheduling constraints:  
 
5. Spatial scales: 
 
5.1. Angular resolution (arcsec): 
       
     Compact configuration (1-2 arcsec) or single-dish 
     
 
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:  
     no  
 
6.4. Subarrays of 12m baseline-ALMA antennas: no 
 
 
7. Frequencies: 
 
7.1. Receiver band: 6 
 
7.2. Lines and Frequencies (GHz):  
      
     CO (2-1) 
      
 
7.3. Spectral resolution (km/s): < 0.05 km/s 
 
7.4. Bandwidth or spectral coverage (km/s or GHz): 
     20 km/s 
 
8. Continuum flux density:  
 
9. Line intensity 
 
9.1. Typical value (K or Jy): 0.0006 K km/s in single-dish mode 
      
 
9.2. Required rms per channel (K or Jy):  
     0.0001 K km/s over 0.6 km/s in single-dish mode  
 
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): 
     
    12 h 
 
12. Total integration time for program (hr):  
 
 
13. Comments on observing strategy :  
     
 
 
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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).