Title  Chemical-dynamical couplings and meteorology in Titan's atmosphere
Pi     E. Lellouch
Time   160 hrs

1. Name of program and authors
Title:  Chemical-dynamical couplings and meteorology in Titan's atmosphere
Authors: E. Lellouch

2. One short paragraph with science goal(s)

Abstract: Titan's atmosphere, rich in hydrocarbons, nitriles and
   oxygenated compounds, is the place for strong chemical-dynamical 
   couplings at these species exhibit strong seasonal variability, 
   are influenced by the global circulation patterns, and participate 
   in the atmospheric thermal balance. ALMA will map at 0.2" species 
   such as CO, HCN, HC3N, CH3CN. Search for new species like CH3CCH, 
   CH2NH, DCN, CxHyCN etc...  will be performed. Stratospheric winds will be 
   measured and thermal profiles retrieved in all strong lines. In additon, continuum
   measurements at a series of frequencies will allow one to map the tropospheric  
   temperature and possible methane humidity.

3. Number of sources : 1
   
   Titan (satellite)


4. Coordinates:

4.1. Rough RA and DEC 

     variable

4.2. Moving target: yes. Satellite ephemerides need to be implemented.

4.3. Time critical: yes (seasonal variability will be investigated)

4.4. Scheduling constraints: (optional)
	

5. Spatial scales:

5.1. Angular resolution (arcsec): 0.2" 

5.2. Range of spatial scales/FOV (arcsec): 0.8" 

     (optional: indicate whether single-field, small mosaic,
     wide-field mosaic...)

5.3. Required pointing accuracy: 0.2"


6. Observational setup

6.1. Single dish total power data: no

     Observing modes for single dish total power:  

     (e.g., nutator switch; frequency switch; position switch;
     on-the-fly mapping; and combinations of the above)

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 5, 6, 7, 8, 9

7.2. Lines and Frequencies (GHz): 

    CO: 230, 345 GHz
    HCN: 354 GHz
    H2O: 183 and/or 325 GHz
    HDO: 226, 464 GHZ
    HC3N,CH3CN: 255 GHz
    TBD molecular searches near 250, 350, 650 GHz

7.3. Spectral resolution (km/s): 0.05 km/s 

7.4. Bandwidth or spectral coverage (km/s or GHz): 2 GHz for broad CO, HCN lines. 0.5 GHz
may be sufficient for other trace species.

8. Continuum flux density:

8.1. Typical value (Jy): 80 K

     (take average value of set of objects)
     (optional: provide range of fluxes for set of objects)

8.2. Required continuum rms (Jy or K): 0.01 K

8.3. Dynamic range within image:

     (from 7.1 and 7.2, but also indicate whether, e.g., weak objects
     next to bright objects)

8.4. Calibration requirements: absolute       1-3% 
                               repeatability  1-3% 
                               relative       1-3% 


9. Line intensity:

9.1. Typical value (K or Jy): 3 K - 30 K

     (take average value of set of objects)
     (optional: provide range of values for set of objects)

9.2. Required rms per channel (K or Jy): 0.5 K

9.3. Spectral dynamic range:

9.4. Calibration requirements: absolute       5 % 
                               repeatability  1-3% 
                               relative       1-3% 


10. Polarization: no 

10.1. Required Stokes parameters:

10.2. Total polarized flux density (Jy):

10.3. Required polarization rms and/or dynamic range:

10.4. Polarization fidelity:

10.5. Required calibration accuracy:


11. Integration time for each observing mode/receiver setting (hr):
Typically 10 hours per line. Wind measurements will be repeated a few (4) times to
search for seasonal variability.


12. Total integration time for program (hr):
About 160 hours 



13. Comments on observing strategy : (optional)

    (e.g. line surveys, Target of Opportunity, Sun, ...):
--------------------------------------------------
Review v2.0:
 
Review 4.1.1-4.1.8

The only question I have with regards to these projects is the use of
ACA cross-correlated with ALMA-12m. Several projects list this option
as 'required' or as 'beneficial', but no arguments are given. 

- When listed as 'required' does this mean that the observations are
  mosaics, and that the ACA is needed to provide the intermediate
  scales? If so, are the cross-correlations with the ALMA-12m antennas
  needed, or could simultaneous ACA-7m-only observations also suffice?

- When listed as 'beneficial' is this purely for S/N reasons or also
  for uv-coverage? The cross-correlation option is fairly demanding on
  the scheduling, and unlikely to be used unless absolutely necessary.