Relation between coordinates parameters of the 30m telescope
SL, 06/2013.
=== Important preliminary remark: for now this page is a sand box where I gather various informations about coordinates variables generated by the 30m telescope control system, which may be useful for the implementation of a new instrument into the system.=== I gathered these information from various documents, Wiki pages, and email exchanges with specialists of the 30m telescope. Ideally I would like that this page contain the list of the various coordinates values delivered by the telescope, with their descriptions and the relations between them. It would good also to centralizes here links to related documents/wiki pages. Of course all this would have to be verified and approved by the 30m specialists (which is not the case for now).
Table of the coordinates parameters generated by the New Control System of the 30m telescope
In particular I list the variables from the antMD.trace category, that are also broadcast on the local network by the Elvin server. The correspondence with the parameters in the IMBFITS files recorded at the end of each scan, and the time stamp information and possibly units of these parameters are also displayed.
antMD.trace. parameter name |
IMBFITS parameter name |
units |
Description |
time of validity of the value |
|
SITELONG |
rad or deg ? |
Telescope longitude |
static |
|
SITELAT |
rad or deg ? |
Telescope latitude |
static |
|
RXHORI |
radians ? |
Nasmyth offset in Pointing Model |
static |
|
RXVERT |
radians ? |
Nasmyth offset in Pointing Model |
static |
|
RXHORICO |
radians ? |
Nasmyth offset in user defined (Pako) |
static |
|
RXVERTCO |
radians ? |
Nasmyth offset in user defined (Pako) |
static |
|
P1 .. P6 |
radians ? |
Pointing Model parameters |
static |
|
CTYPE1 |
string |
Source coordinate system for BASELONG (e.g. AZ, RA, etc.) |
static |
|
CTYPE2 |
string |
Source coordinate system for BASELAT (e.g. EL, DEC, etc.) |
static |
|
SYSTEMOF |
string |
System in which offsets (LONGOFF/LATOFF) are reported |
static |
|
LONGOBJ |
rad or deg ? |
Longitude of the source in the chosen coordinate system (RA or AZ etc.) |
predicted value at TimeStamp + 2s |
|
LATOBJ |
rad or deg ? |
Latitude of the source in the chosen coordinate system (DEC or EL etc.) |
predicted value at TimeStamp + 2s |
timeStamp |
|
seconds ? |
time at which the antMD message is sent |
|
slowRate |
|
Hz |
Frequency at which the coordinates data are generated |
|
LST |
LST |
seconds ? |
Local Sideral Time |
predicted value at TimeStamp + 2s |
MJD |
MJD |
days |
Modified Julian Day |
predicted value at TimeStamp + 2s |
basisLat |
BASELONG |
radians ? |
Actual longitude in the chosen coordinate system (RA or AZ etc.) |
predicted value at TimeStamp + 2s |
basisLong |
BASELAT |
radians ? |
Actual latitude in the chosen coordinate system (DEC or EL etc.) |
predicted value at TimeStamp + 2s |
xOffset |
LONFOFF |
radians ? |
Scan pattern longitude offset from the source in SYSTEMOF (RA or AZ etc.) |
predicted value at TimeStamp + 2s |
yOffset |
LATOFF |
radians ? |
Scan pattern latitude offset from the source in SYSTEMOF (DEC or EL etc.) |
predicted value at TimeStamp + 2s |
actualAz |
CAZIMUTH |
radians ? |
"Commanded" azimuth |
TimeStamp-1s/slowRate |
actualEl |
CELEVATION |
radians ? |
"Commanded" elevation |
TimeStamp-1s/slowRate |
trackAz |
AZIMUTH |
radians ? |
Real azimuth in the encoder reference |
TimeStamp-1s/slowRate |
trackEl |
ELEVATION |
radians ? |
Real elevation in the encoder reference |
TimeStamp-1s/slowRate |
TRACKING_AZ |
radians ? |
Azimuth RMS tracking error (sampling with fastTrace = 128 Hz) |
TimeStamp-1s/slowRate |
|
TRACKING_EL |
radians ? |
Elevation RMS tracking error (sampling with fastTrace = 128 Hz) |
TimeStamp-1s/slowRate |
|
|
radians ? |
Azimuth Max tracking error (sampling with fastTrace = 128 Hz) |
TimeStamp-1s/slowRate |
|
|
radians ? |
Elevation Max tracking error (sampling with fastTrace = 128 Hz) |
TimeStamp-1s/slowRate |
|
|
radians ? |
Azimuth Min tracking error (sampling with fastTrace = 128 Hz) |
TimeStamp-1s/slowRate |
|
|
radians ? |
Elevation Min tracking error (sampling with fastTrace = 128 Hz) |
TimeStamp-1s/slowRate |
- Az(El)_real = Az(El)_expected + TRACKING_AZ(EL); Az(El)_expected = AZIMUTH(ELEVATION) ? but TRACKING_AZ(EL) and AZIMUTH(ELEVATION) are in encoder units {in IMBF-antenna}, so use BASELONG(BASELAT) [= source position in the system defined in CTYPE1(CTYPE2) {in IMBF-scan}] and LONFOFF(LATOFF) [= offset to the source position] ? Note that CAZIMUTH(CELEVATION) seem to be the intended coordinates, but the commanded ones are these corrected by the inclinometer values (and possible other corrections).