VIII. Post-Cryo Data Release

The scan_id has the general form SSSSSx, where

• SSSSS is a zero-filled, five-digit integer that is twice the WISE orbit number. The orbit number increments each time the flight system passes the north ecliptic pole (NEP). Orbit number 1 was defined to start with the fictitious NEP passage immediately prior to WISE launch.


• x   is a letter assigned based on sequential count of scans started in a specific half-orbit. The first scan has x="a", the next x="b", up to a maximum of x="d" for scans in the Post-Cryo Release.

The first scan whose data are used in the Post-Cryo processing is scan 08745a. This was the first scan after the NEP crossing in the 4372nd WISE orbit. The final scan included in the Post-Cryo Release is 12514a, the first scan after the SEP crossing in the 6257th WISE orbit.

The frameset number is computed based on time bins which count from the scan start time:

where

• int[] means truncate to an integer
• frame_utc is the nominal frame exposure center UTC (when the boresite crosses the image center) in seconds
• dt_beg is 4.4s. This is a nominal offset to approximate when the exposure began
• scan_start_utc is the scan start time in seconds
• bin_size is 10s.

For example, a frame with a start time 1234 secs after the scan start time would have a frame number of 124.

N.B.

• Frame_num is not a frameset sequence number


• As a result of using a 10 sec bin, every 11th frame skips a number, so it is normal to see breaks in the frame numbering and it doesn't indicate missing data.


• Because frameset numbering is based on the predicted scan start time from the survey plan, and because frameset data may not start being acquired until well after the start of the scan, frameset numbers often do not start at 1 for a scan.