Title  A complete picture of an Earth-grazing short-period comet 
Pi     D. Bockelee-Morvan
Time   168 hrs

1. Name of program and authors 
   A complete picture of an Earth-grazing short-period comet 
   Authors: D. Bockelee-Morvan, N. Biver, J. Crovisier, J. Boissier 
 
2. One short paragraph with science goal(s) 
   With ALMA it will be possible to determine the relative  
   abundances of a number of species in the coma of a short-period  
   Earth-grazing comet, for comparison with determinations in Oort  
   cloud (long-period) comets.  All species identified in comet  
   Hale-Bopp should be detected, leading to the first extensive chemical  
   characterisation of a Jupiter family comet. In addition, several  
   isotopic species will be detected (e.g. HDO, DCN, H13CN, HC15N, CS 
   C- and S isotopes), whose abundances are key indicators of the origin of  
   cometary material.  Mapping of a few key lines will be made for  
   comparison of the gas jets morphology to dust jets, and to identify  
   molecules released by grains or formed by molecule decomposition in  
   the coma. Simultaneous monitoring of CO and HCN over a few days is  
   crucial to investigate sublimation and gas dynamic processes at  
   the surface and above the nucleus as the nucleus is rotating.  
   Continuum maps will provide the dust distribution of large sized  
   particles and the dust-to-gas ratio. Attempt will be made to detect  
   the nucleus (probably of order ~1 km radius) on the largest  
   baselines. 
 
3. Number of sources  
   Year dependent. 
   One in 2010 (103P/Hartley 2), one in 2011 (45P/Honda-Mrkos-Padjusakova) 
   though full ALMA not available at that time.  
 
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  
 
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: 
    Continuum in parallel to line observations 
    
8.1. Typical value (Jy) 
     nucleus : a few mJy for the 2010 and 2011 targets taken as exemples  
 
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 0.1 to 20 K km/s (HCN4-3) in compact 
     configuration 
      
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 :  
     Line mapping requires ALMA to be in compact configuration. Nucleus 
     investigation requires more extended configurations. 
     So, depending of the priority given to one or the other topic, and given  
     the fact that the passage of short-period comets is predictable 
     (in contrast to long-period comets), it would highly desirable 
     to have ALMA in the desired (or as close as possible) configuration 
     at the time of the comet passage. 
      
 
 
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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).