Polar Ultraviolet Imager, Key Parameters

https://doi.org/10.48322/1ac1-5c88

2023-07-30 12:34:56.789

The Ultraviolet Imager (UVI) is a small camera that detected and produced images of the ultraviolet light of the aurora, day and night. Key Parameter (KP) images are calculated at nominal 5-10 minute intervals at spacecraft altitudes above 6 Re. The UVI KP image is background subtracted and calibrated to radiance values (photon cm^-2 cm^-1). The data is a rectangular two-dimensional array (228 rows x 200 columns). Only a circular region of the rectangular array contains valid image data. The UVI KP Image Archive (http://tideuvira.nsstc.nasa.gov/uvi/kpgs-Data.htm) allows the user to look at all the KP Mosaics for a selected month. The gif or png plot files contain the up to 35 KP images taken with the LBHL filter. Reference images are also provided showing the location of the UVI field of view relative to continental outlines.

spase://VMO/NumericalData/POLAR/UVI/K0_CDF

spase://VSPO/NumericalData/POLAR/UVI/K0_CDF

Online

Open

CDF

Online

Open

CSV

FUV Image

IMAGE_DATA

Far Ultraviolet Image - 8 degree full width (228 x 200 pixels)

The UVI field of view is circular with an 8 degree full width. The circular image is stored in IMAGE_DATA as a rectangular array of 228 rows and 200 columns. Consequently, the corners of each image contain non-image data. The non-active corner pixel locations are identified by a corner fill value = -128. The image is oriented such that the direction of decreasing row number points along the spacecraft spin axis. The direction of decreasing column number points to the outboard direction (relative to the spin axis). The orientation is the same for both detectors.

photon cm^-2 s^-1

Time Line

Epoch

Image time.

The time in EPOCH and Time_PB5 refer to the center of the image in IMAGE_DATA. There is an offset of up to 8 major frames between the beginning of the image exposure and the ATC telemetry time stamp. The times shown here are corrected for this and describe the actual time of exposure.

ms

01-Jan-1990 00:00:00.000

31-Dec-2020 23:59:59.000

-1.0E31

Time Line

Time_PB5

Image time.

The time in EPOCH and Time_PB5 refer to the center of the image in IMAGE_DATA. There is an offset of up to 8 major frames between the beginning of the image exposure and the ATC telemetry time stamp. The times shown here are corrected for this and describe the actual time of exposure.

Relative beginning of image

IMG_MINUS_MSEC

The start of the image, measured from EPOCH/Time_PB5.

The beginning and ending time of the image is specified in msec relative to the time in EPOCH and Time_PB5 by IMG_MINUS_MSEC and IMG_PLUS_MSEC, respectively.

ms

-1800000.0

0.0

-1.0E31

Relative end of image

IMG_PLUS_MSEC

The end of the image, measured from EPOCH/Time_PB5.

The beginning and ending time of the image is specified in msec relative to the time in EPOCH and Time_PB5 by IMG_MINUS_MSEC and IMG_PLUS_MSEC, respectively.

ms

0.0

1800000.0

-1.0E31

Post Gap Flag

POST_GAP_FLAG

Explanation of preceding gap.

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; 2 = Missing Data; 3 = Noisy Data; 4-9 = undefined; 10 = High voltage not enabled; 11 = gain set to zero; 12 =The first minor frame containing UVI housekeeping was zero filled 13 = Unable to sync with telemetry stream; 14 = No background images were present; 15 = Requested filter setting was not present; 16 = Spacecraft was near perigee pass where no kp's are generated; 17 = Despun platform was pointing away from the earth; 18 = Image data lay outside requested process window (Not used for production); 19 = Unknown. Note that long gaps may be caused by multiple events. POST_GAP_FLAG attempts to represent the most severe event contributing to the gap. Also, since each image frame 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 may be several minutes apart. This condition is not trapped and will result in an unknown value for the post gap flag.

0

19

-2147483648

Quality Flag

QUALITY_FLAG

Bit-mapped quality indicator.

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: 0 = No errors or quality conditions; 1 = an error occurred writing an SFDU comment; 2 = image time was outside of selected processing window; 4 = some level zero minor frames had fill values; 8 = some level zero minor frames had sync errors; 10 = the image single frame integration period could not be determined due to bad telemetry (assumed to be 4 major frames); 20 = the despun platform was in motion or had not settled down from a motion; 40 = the pointing calculations have not been validated or may be unreliable; 80 = the time flags for this image may be unreliable; 100 = there was an error decode star mode data; 200 =some major frames were missing but an image could be partially reconstructed; 400 = calibration data is missing or otherwise invalid; 800 = a background image could not be found; 1000 = the requested output image could not be found.

0

2147483647

-2147483648

Nominal Time Between Records

NOMINAL_OUTPUT_PERIOD

Nominal time between output records.

This is the nominal time between output records. The actual output spacing will vary depending on the nature of the observing sequences being run.

minutes

0

300

-2147483648

Primary/secondary detectors

SYSTEM

Operating system.

UVI has two independent systems. PRIMARY: +1, SECONDARY: -1

-1

1

-2147483648

Observing sequence

SEQ

Predefined sequence of observations. Definitions will change over mission.

0

49

-2147483648

Observing mode

MODE

Instrument operating mode.

(1=Normal, 2=Star, 3=Idle) Normal mode produces one 200 x 228 image every 4 major frames. Star mode produces multiple miniframe images every major frame. Idle mode produces no image output.

1

3

-2147483648

Detector Gain Setting

GAIN

Detector gain setting

0=off, 16=highest sensitivity

0

16

-2147483648

Aperture door position

DOOR

Aperture door position

(OPEN: +1, CLOSED: -1) MgF2 window in door allows viewing when closed.

-1

1

-2147483648

GCI Spacecraft Position Vector

GCI_POSITION

Spacecraft Position in GCI, 3 comp.

Copied from S/C orbit file.

km

GCI Spacecraft Attitude Vector

ATTITUDE

Spacecraft Attitude in GCI, 3 comp.

Calculated from S/C attitude file.

GCI Sun Vector

GCI_SUN

Sun Position in GCI, 3 comp.

Vector pointing to sun.

km

GCI Look Direction

GCI_LOOK_DIR

Unit vector along field of view.

GCI_LOOK_DIR is a unit vector in GCI coordinates pointing from the spacecraft along the center of the UVI line of sight. An external utility can be used to calculate latitude and longitude for any pixel of the UVI image.The pointing utility can be found on the UVI WWW home page

DSP Nadir Offset Angle

DSP_ANGLE

Offset angle of despun platform from nadir.

Positive in direction opposite of spacecraft rotation.

Degree

-180.0

180.0

-1.0E31

Image Type

FILTER

Filter selection.

1304=2, 1356=3, LBHS=4, LBHL=5, SOLR=6

2

6

-2147483648

Geodetic Latitude

GEODETIC_LAT

Geodetic latitude for IMAGE_DATA (23 x 20 pixels)

Sparse matrices (every 10 pixels) of latitude and longitude are given in GEODETIC_LAT and GEODETIC_LONG, respectively. Latitude and longitude are given in geodetic coordinates (determined from the normal to the assumed surface of the earth [assumed to be an ellipsoid of revolution]) and not in geocentric coordinates (determined relative to the center of the earth).

Degrees

Geodetic Longitude

GEODETIC_LONG

Geodetic longitude for IMAGE_DATA (23 x 20 pixels)

Sparse matrices (every 10 pixels) of latitude and longitude are given in GEODETIC_LAT and GEODETIC_LONG, respectively. Latitude and longitude are given in geodetic coordinates (determined from the normal to the assumed surface of the earth [assumed to be an ellipsoid of revolution]) and not in geocentric coordinates (determined relative to the center of the earth).

Degrees

Row Number

ptr_row

Row Number

pixel

1.0

228.0

-1.0E31

Column Number

ptr_col

Column Number

pixel

1.0

200.0

-1.0E31

Row Number

row

Row Number

pixel

1.0

228.0

-1.0E31

Column Number

ptr_col

Column Number

pixel

1.0

200.0

-1.0E31