| terms |
description |
AST
|
Atlantic Standard Time. This is arecibo's local time zone (all
year since puerto rico does not switch for daylight savings). |
group,record
|
A single integration is called a group. Groups
can contain multiple records. Each record contains a header
followed by data. Example:
-
A 5 minute scan using 4 correlator boards at different frequencies is written
to disc using 1 second integrations. Each 1 second output is a group.
There will be 300 groups in this scan. Each group contains
4 records (one for each correlator board). Each record will
have a header followed by the data for that correlator board.
WARNING: the documentation has evolved and now often uses record
in place of group. This is probably ok since the original distinction between
group
and record came from tape drives where the above group would
have taken 4 physical records on the tape (at least with 9 track
tapes). |
| pattern |
|
| position switch |
|
scan
|
a set of integrations (records) contiguous in time. Normally the configuration
of the system will remain constant for a scan. Examples are:
-
an on/off position switch pattern with a cal on, off. This normally take
4 scans: tracking on src, tracking off src, calOn integration, calOff
Integration.
-
mapping a region of the sky. Each strip of the map will be a scan.
|
scan number
|
scan numbers uniquely identify scans. They are 32 bit
integers (which hold numbers up to 2 billion). The format is ydddxxxxx.
-
y is the last digit of the year (so scan numbers repeat every 10
years)
-
ddd is the daynumber of the year (AST).
-
xxxxx starts at 1 at the start of each AST day and gets incremented
each scan. If the computer reboots then xxxxx is set to the current seconds
from midnight.
Data reduction routines usually use scan numbers to identify the
data to process. |
| scan list |
|
| table |
|