ISOCAM Interactive Analysis User's Manual Version 5.0 - ISO - ESA

15.2. OBSERVATION DATA STRUCTURES 165
15.2.2 Science CAM data (SCD)
Following the definition of an SCD at the beginning of Section 15.2 we will look at where the
FRAMEs, IMAGEs and CAM parameters are stored. All of these data are stored in the fields of
the SCD. Those fields unique to the SCD are listed here, the rest being listed in Section 15.2.1.
1. N RASTER: The position of the STATE in a raster in the N direction (see Appendix E).
The first position corresponds to N RASTER=1. For non-raster SCDs N RASTER is
always one. Type: integer.
2. M RASTER: The position of the STATE in a raster in the M direction (see Appendix E).
The first position corresponds to M RASTER=1. For non-raster SCDs N RASTER is
always one. Type: integer.
3. ASNUMBER: Its meaning depends on the type of on-board processing 3 , as indicated
by the field .CAL.OBC (see Section 15.2.2.20), which is performed. Type: integer.
• .CAL.OBC=0 No on-board processing. ASNUMBER will also be 0.
• .CAL.OBC=1 IMAGEs computed on-board and accumulated before transmission
to ground. ASNUMBER indicates the number of on-board accumulations:
value description
0 no accumulation i.e. EOI and RESET FRAMEs in telemetry.
1 two IMAGEs accumulated
2 three IMAGEs accumulated
. .
15 16 IMAGES accumulated
• .CAL.OBC=2 Only sampled IMAGEs in telemetry. ASNUMBER indicates the
sampling frequency. E.g. ASNUMBER=4 implies that 1 in 4 IMAGEs are transmitted
to ground.
4. CRPIX1: RA reference pixel of IMAGE in FITS convention 4 . Type: float.
5. CRPIX2: DEC reference pixel of IMAGE in FITS convention 4 . Type: float.
6. RA: RA(J2000) of CRPIX1. Type: double. Unit: decimal degrees.
7. DEC: DEC(J2000) of CRPIX2. Type: double. Unit: decimal degrees.
8. ROLL: The spacecraft roll (see Appendix E). Type: double. Unit: decimal degrees.
9. ENTWHL: Entrance wheel position (see the ISOCAM Handbook for possible values of
ENTWHL.). Type: string. e.g. ‘HOLE’.
10. SELWHL: Selection wheel position (see the ISOCAM Handbook for possible values of
ENTWHL.). Type: string. e.g. ‘FABRY MIRROR LW’.
3 Usually, on-board processing only takes place when TINT=0.28s or for CAM parallel data.
4 By FITS convention (CRPIX1, CRPIX2) are the coordinates of the centre of the reference pixel, counting
from 1. E.g. If the reference pixel is indexed in IDL as (9, 9), then CRPIX1=10.5 and CRPIX2=10.5.