P74-803: Near-Earth-object polarimetry and astrometry for planetary defence

Imaging polarimetry requiring differential tracking.

This proposal includes 30h Monitoring observations on fixed dates (see schedule below) for roughly 5 hours per month, as well as ToO/SoftToO observations triggered on any date (6 hours).

Instrument setup required for ALFOSC linear polarimetry

• Filter: R (#76)
• Aperture wheel: Calcite
• FAPOL: lambda/2

Monitoring schedule P74

       Date, Prop-ID,       UT-window,  Duration,  Instrument,  Any comment

 01-10-2026,  74-803,     [ECT]-20:30,     00:25,      ALFOSC,  Phaethon ph104
 01-10-2026,  74-803,     23:30-[SCT],     00:25,      ALFOSC,  2001CB21 ph101 + standards
 03-10-2026,  74-803,     [ECT]-21:20,     00:20,      ALFOSC,  Phaethon ph95
 06-10-2026,  74-803,     [ECT]-22:00,     00:20,      ALFOSC,  Phaethon ph90
 06-10-2026,  74-803,     [ECT]-[SCT],     00:20,      ALFOSC,  2001CB21 ph58
 10-10-2026,  74-803,     [ECT]-[SCT],     00:20,      ALFOSC,  2001CB21 ph45
 18-10-2026,  74-803,     03:00-[SAT],     1:15,       ALFOSC,  Zoozve ph98 + standards
 26-10-2026,  74-803,     [ENT]-04:30,     00:40,      ALFOSC,  2001CB21 ph32
 26-10-2026,  74-803,     [ENT]-[SNT],     00:40,      ALFOSC,  Zoozve ph78
 30-10-2026,  74-803,     [ENT]-[SNT],     00:35,      ALFOSC,  Zoozve ph65 + standards

 02-11-2026,  74-803,     [EAT]-04:00,     1:00,       ALFOSC,  1999TF211, ph28
 04-11-2026,  74-803,     [ENT]-03:00,     00:30,      ALFOSC,  Zoozve ph52
 08-11-2026,  74-803,     23:00-[SAT],     1:00,       ALFOSC,  1998WZ6 ph28 + standards
 26-11-2026,  74-803,     02:30-[SNT],     00:40,      ALFOSC,  1998WT24 ph75 + standards
 29-11-2026,  74-803,     21:00-[SAT],     00:40,      ALFOSC,  1998WZ6 ph17

Daytime domeflat observing instructions:

• Biases are taken as part of the automatic calibration script alfosc-calibs in the morning

• NB! Afternoon dome-flats with the full polarimetry setup as follows (set off some afternoon time for this):
  
  
  1. power-on the telescope, place it and open mirror covers with the TCS commands alt 45 and o-m-c
     
     
  2. tcs.setup-tel-alfosc
     
     
  3. Place the halogen "FF lamp" under the telescope and plug in
     
     
  4. alfosc.propid 74-803 (puts the files in the right directory)
     
     
  5. alfosc.carriage in
     
     
  6. alfosc.wheels -s Calcite -f 76
     
     
  7. alfosc.focus-offset
     
     
  8. alfosc.resetxy; alfosc.polwin; alfosc.bin 2
     
     
  9. Take a test exposure to determine the exptime t that gives between 300-400kADUs
     
     
  10. In order to make 3 cycles of 16 angles each with exptime t, do:
      alfosc.linpolexpose 16 domeflat t 3 -nowindow; astrowakeup
      
      
  11. When finished, do alfosc.carriage out, alfosc.resetxy, and alfosc.allopen
      
      
  12. When setup is ready, reset focus: alfosc.focus-offset
      
      
  13. Close mirror covers and park the telescope with the TCS commands c-m-c and zenith
      
      
  14. In the dome disconnect the "FF lamp" and store it (NB! it can be hot!)
      
      
  15. If it takes more than about 1 hour before your evening observations start, do power-off on the TCS.
      
      

Observing instructions:

1. If you are not already using ALFOSC, go to the desktop where the ALFOSC Sequencer is running, and change the telescope settings with the command:
     tcs.setup-tel-alfosc

2. Go to the directory
     cd ~/scripts/74-803
   List the available scripts
     ls -lrt

   All OBs to be observed will have tonight's date (i.e. start of the night) in their name.
   Note that in addition to the target there can also be standard star polarimetry OBs

3. Start the target OB script, when it tells you to do the pointing, go to another sequencer window to run the ASTEPH tool

4. The different target speeds may require 3 different observing modes:
   • For rates < [70 ("/h) x OB-execution (h)], typically this command is used (auto-guiding):
     tcs.asteph -n targetname
     

   • For rates > [70 ("/h) x OB-execution (h)] either of the following two are used (auto-guiding & repositioning):
     tcs.asteph -m optimal-ll -n targetname
     tcs.asteph -m optimal-lr -n targetname

   • For rates >> 800 ("/h) blind tracking with update of rates may be requested:
     tcs.asteph_new -g update -n targetname

   ASTEPH connects to JPL Horizon to get the actual position and rates. See examples in green color below.

   In the case of using the optimal modes you also get the best setting of the field-rotation to optimize guide star area for repositioning.

   FOR EXPERTS: You can check both optimal-ll and optimal-lr (ASTEPH only outputs information on the screen)
   To optimize slewing time select the case that involves less turning of the rotator (the flag -f xx.xx gives field-rotation in the guide-object command).

       
   > tcs.asteph -n 68548
   ...
   These tasks should be given to the TCS:
   ***************************
   tcs.append-object 68548_2001_XR31-1 17 06 18.91 +78 39 35.7 2000.0 0.0 0.0 17.314
   tcs.ag-off
   tcs.guide-object 68548_2001_XR31-1
   tcs.reposition-guide-probe 193.864 41.25260
   
   > tcs.asteph -m optimal-lr -n K07S06Q
   ...
   These tasks should be given to the TCS:
   ***************************
   tcs.append-object 2007_SQ6-1010 03 20 02.18 +09 15 10.5 2000.0 0.0 0.0 17.709
   tcs.ag-off
   tcs.tcs-command "instrument-name ALFOSC ALFOSC-LR"; tcs.guide-object -f 57.173 2007_SQ6-1010
   tcs.reposition-guide-probe 241.628 -374.546
   
   > tcs.asteph_new -g update -n 2023 SZ3
   ...
   These tasks should be given to the TCS:
   ***************************
   ### IN THE FIRST SEQUENCER WINDOW ###
   tcs.append-object 2023_SZ3-1737 01 15 47.49 -31 28 29.2 2000.0 0.0 0.0 18.615
   tcs.ag-off
   tcs.guide-object
   #### IN THE SECOND SEQUENCER WINDOW ####
   hitandrun  2023_SZ3-1737  hitandrun.input  '2026-Sep-22 17:38:01.000'  10 3600 ima
   

5. The next step is to point the telescope to the target in question.
   • For the first two cases, cut and paste the 4 TCS commands into the sequencer window.
     The 4th command starts the differential tracking and autoguiding.

   • for the 3rd case (-g update) you need to do as follows:
     1. open a third sequencer terminal and cd scripts/74-803
     2. ignore the 3 first TCS commands
     3. run hitandrun as output by ASTEPH, BUT make sure the UT time is set 2-3 min into the future
     4. when guiding is OK, press RETURN (it is only used for pointing correction)
     5. now wait until the script does ag-off and starts updating rates

6. For all cases, you are now ready press return where the OB script is running to start taking data.

For more general information on how this works, see the section "Moving Targets" in the ALFOSC Cookbook.

At the end of the night:

• When all OBs are done (check also for standard star OBs with today's date ), please, close them.

• Please, fill in the Mon tracking log.

• Remember to run alfosc-calibs ALF*** in the morning, where the input parameter is the file prefix.

Should any of the observations have been carried out using the OB system, you will find additional information HERE