The hardware interfaces are described in [AD 08].
The available commands for controlling M6 are described in the STRAP User Manual [RD 07].
The control of M6 tilt angles is only possible when STRAP is
running in Open Loop (no correction sent to M6). In close loop, the
setting of M6 tilt angles has little effect.
The M6 tilt angles are expressed in M6 coordinate system, which is rotating
w.r.t. the APD plane (Interaction Matrix) and sky coordinates.
| Item | From | To | Command/Action | Parameter | Unit | Note | |
|---|---|---|---|---|---|---|---|
| Command | Reply | ||||||
| CENTER M6: | |||||||
| 1 | ATCS | STRAP | Write tip-tilt angles to STRAP LCU database Send command NWSETUP |
spotOffsetX/Y=(0,0) |
arcsec |
1 | |
| SET M6 ABSOLUTE TILT: | |||||||
| 2 | ATCS | STRAP | Write absolute tip-tilt angles to STRAP LCU database Send command NWSETUP |
spotOffsetX/Y=(a,b) |
arcsec |
2 | |
| SET M6 RELATIVE TILT: | |||||||
| 3 | ATCS | STRAP |
Read absolute tip-tilt angles from STRAP LCU database Add tip-tilt offsets to the absolute angles Write absolute tip-tilt angles to STRAP LCU database Send command NWSETUP |
(Da,Db) spotOffsetX/Y=(a,b) |
spotOffsetX/Y=(a,b) |
arcsec arcsec arcsec |
3 |
| GET M6 ABSOLUTE TILT: | |||||||
| 4 | ATCS | STRAP |
Send command GIVDIAG Read absolute tip-tilt angles from STRAP LCU database |
spotOffsetX/Y=(a,b) |
arcsec |
4 | |
Note 1: This command is not mandatory in observation mode, since the re-centering of M6 is performed automatically as a consequence of the counter-offsetting of the telescope axes (average tip-tilt offset sent to M6 from STRAP).
Note 2: The tilting is necessary for chopping, since it is not supported by the STRAP software/firmware. ATCS needs to set the M6 tilt angles from the chopping loop. The tilting of M6 has little effect when the loop is closed since STRAP will overwrite the angles at the next integration.
Note 3: This feature is not supported by STRAP. This could be solved by adding the relative angles to the actual ones, assumed the database values reflect exactly the effective tip-tilt angles of M6.
Note4: This function is mandatory for the M6 Control Loop. It is useful for maintenance and tests, since analog telemetry values of the M6 tip-tilt are not available in the current LCU configuration (AIO board would be required on the Sensor LCU).
The following commands shall be preferred:
| Item | From | To | Command/Action | Parameter | Unit | Note | |
|---|---|---|---|---|---|---|---|
| Command | Reply | ||||||
| 1 | ATCS | STRAP | Send command CENTER | ||||
| 2 | ATCS | STRAP | Send command TILTABS | (a,b) | arcsec | ||
| 3 | ATCS | STRAP | Send command TILTREL | (Da,Db) | arcsec | ||
| 4 | ATCS | STRAP | Send command GETTILT | (a,b) | arcsec | ||
Last modified: Wed Nov 24 11:50:10 MET 1999