JCMT Telescope Control System

1. JCMT Telescope Control System Nick Rees

2. Basic Functionality • TARGET • OFFSET • SCAN • ROTATOR • CHOPPING • JIGGLING • MECHANISMS (Slew/Wait/Track control) • POINTING (Log,Adjust) • Status enquiry. • Parameters

3. TARGET • Defines a basic reference point for the observation. • Can either be a major planet, Sidereal (RA/Dec like) , mount (Alt/Az like) or elements (minor planets). • Major planet specified by name only and the JPL Ephemeris is used. • All except a major planet can have additional motion (e.g. for planetary satellites). • RA/Dec like coordinates can specify a target radial velocity. (RV is calculated for other types). • Intend to allow multiple reference points to be defined (e.g. calibration position).

4. OFFSET • Specifies a delta from the current target. • Used for observing grids and sky positions. • Can be specified in virtually any coordinate system, including mount and focal plane. • Can be specified as direct coordinates, or as a projection.

5. SCAN • Used to specify raster scans of rectangular areas. • Currently TCS only handles one row, but we now propose to do calculations for a rectangular area. • TODD will query TCS for scan parameters for next row, then calculate number of samples. • Intend to support rectangular area defined in one system, and scans performed in another (current DEFINE_SCAN definition doesn’t do this, but will change). • Will be an approximation using Cartesian projected coordinates at the current time,

6. ROTATOR • Rotator system can be TRACKING, AZEL or FIXED. • Just specify position angle in the current system. • Intending to support tracking/update/not tracking modes.

7. CHOPPING • Current document reflects both lower level actions (DEF_CHOPBEAM) and higher level one (SETUP_CHOPBEAMS). Will probably only support high level one. • Can be specified in current tracking, AZEL, MOUNT or Focal Plane coords. • Will alter definition to be (r,theta) coords. • Will define both nod beams and secondary chop beams.

8. JIGGLING • Used for both focussing, pointing and image sampling. • Same (but independent) coordinate systems as Chopping. • Should we implement this in XML and the CONFIGURE or SEQUENCE action?

9. MECHANISMS • Instrument dependencies handled by SET_FOC_STATION. • Moves TMU • Updates pointing model • Rotator, secondary tables can be set to update continuously or update only on demand.

10. POINTING • Can adjust pointing as a result of a pointing measurement. • Can log pointing information.

11. Status enquiry • Current status can be monitored in various ways: • GET_STATUS action (specify events you are interested in). • Parameter monitoring • Polling parameters • Specific actions (GET_TELESCOPE, GET_BASE etc).

12. Parameters • RTS_POSN • SEQ_NUMBER: Sequence number, • TAI: Average atomic time of integration • C1,C2: Telescope position in current tracking coordinates, • TC1,TC2: Target position in current tracking coordinates, • PA: Angle between focal plane and current tracking coordinates. • Radial Velocities (RV, RV_BASE). • Various components of radial velocity plus: • DOPPLER: Doppler correction for current target’s specified radial velocity.

13. Questions • Should we move to an XML configuration? • Specifies focal station, targets, scan area sizes, chop angles, jiggle patterns and rotator angle. • Only commands are those essential for sequence: • Get the next scan row length. • Perform a scan row. • Perform an offset. • Perform a slew to another target. • Update mechanism movements. • Pointing adjustments • Nod to beam • How do we handle pointing sources?

14. Details • Web pages