KPGS- Key Parameters

POST_GAP_FLAG
Required by ISTP Standard. A gap is defined if the time between records is greater than twice the nominal output time (NOMINAL_OUTPUT_PERIOD). The following values are defined for POST_GAP_FLAG:

• O = No Gap
• 1 = Wrong Mode. This includes both instrument and spacecraft telemetry mode. The UVI KPGS process data for only normal instrument mode transmitted in 9.2 second telemetry mode.
• 2 = Missing Data
• 3 = Noisy Data. Not trapped by the UVI KPGS.
• 4-9 = undefined
• 10 = High voltage not enabled. No image can be produced when the high voltage is disabled.
• 11 = Instrument gain set to 0. No image can be produced when the gain is zeroed.
• 12 = The first minor frame containing UVI housekeeping was zero filled. The first minor frame contains critical parameters used to process the image data. The data cannot be processed if the first minor frame is corrupted.
• 13 = Unable to sync with telemetry stream.
• 14 = No background images were present. Image will be processed without background subtraction. This will seriously comprimise the validity of the intensity calibration and is flagged by QUALITY_FLAG.
• 15 = Requested filter setting was not present. Once a gap has been declared the current image is output, regardless of the requested filter setting.
• 16 = Spacecraft was at lower altitudes where image quality is limited due to noise from passage through the radiation belts.
• 17 = The despun platform was pointed away from the earth, preventing images of the auroral region.
• 18 = Image data lay outside requested process window. This is a debug mode and should not be seen in normal production data.
• 19 = Unknown.

Also, since each image frame typically requires a minimum of 4 major frames (36.8 s) very short values of NOMINAL_OUTPUT_PERIOD on the order of 1 minute may always encounter a gap since the desired images will be several minutes apart. This condition is not trapped and will result in an unknown value for the post gap flag.

The utility GAPdecode from the UVI Utilities page can be used to decode the gap values.

QUALITY_FLAG
Required by ISTP Standard. QUALITY_FLAG is a bit-mapped flag in which each bit corresponds to a single quality condition. The most significant bit (minus sign) is not used. Consequently up to 31 different quality conditions can be simultaneously flagged. The flags are ordered in severity with increasing bit position. The following _hexadecimal_ values have been defined for QUALITY_FLAG:

• 0x = No errors or quality conditions.
• 1x = An error occurred writing an SFDU comment.
• 2x = Image time was outside of selected processing window. This indicates a debug condition and should not be seen for production data.
• 4x = Some level zero minor frames had fill values. This can result in single pixel errors (streaks, dropouts, spikes, etc.). If housekeeping values are lost some of the image information may be lost.
• 8x = Some level zero minor frames had sync errors. This can result in single pixel errors (streaks, dropouts, spikes, etc.). If housekeeping values are lost some of the image information may be lost.
• 10x = The image single frame integration period could not be determined due to bad telemetry and was assumed to be 4 major frames. This is the typical integration period but may be too long by one or two major frames following a mechanism movement.
• 20x = The despun platform was in motion or had not settled down from a motion. The image may be blurred or may not reflect the higest spatial resolution possible with the instrument.
• 40x = The pointing calculations have not been validated or may be unreliable for other reasons.
• 80x = The time tags for this image may be unreliable.
• 100x = There was an error decoding star mode data.
• 200x = Some major frames were missing but an image could be partially reconstructed.
• 400x = Calibration data is missing or otherwise invalid. An uncalibrated image is shown. For early mission data this may indicate that the calibration data is not yet validated and should be used with caution.
• 800x = A background image could not be found. No background subtraction was performed. This compromises the validity of the calibration.
• 1000x = The requested output image could not be found. An available image was output instead.