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CALIPSO - Data User’s Guide - IIR Level 1 Product - Versions 2.00 and 2.01


10-01-2020: Version 2.01
A minor version bump (+0.01) has been applied to all CALIPSO data products due to a required upgrade to the operating system on the CALIPSO production cluster. All algorithms were re-compiled to process in this new environment with no change to the underlying science algorithms or inputs.


Introduction

This document provides a description of the level 1B IIR radiances product DP1.2, as described in the CALIPSO Data Products Catalog (Version 4.30) (PDF).

The IIR Level 1B data standard product contains a half orbit of geolocated and calibrated radiances. Image data are registered to a 1 km grid centered on the lidar track. The Level 1B data product is written in HDF.

The maximum number of IIR sequences processed in one orbit is 729, which equates to 1 sequence every 8.184 seconds. A sequence is a collection of 6 images: 3 Earth views and 3 calibration views (deep space or blackbody). Image data are registered to a 1 km grid centered on the lidar track. Each grid line occurs every 3 lidar shots, or 40,095 grid lines per orbit (20,048 per half orbit).

Related Publications:

  • Corlay, G., Arnolfo, M.-C. Bret-Dibat, T., Lifermann, A., and Pelon, J.: “The Infrared Imaging Radiometer for PICASSO-CENA”, CNES Tech. Doc., 14 pp., available at: https://calipso.cnes.fr/sites/default/files/migration/smsc/calipso/IIR_ICSO00_S2-06.pdf, 2000.
     
  • Garnier, A., Scott, N. A., Pelon, J., Armante, R., Crépeau, L., Six, B., and Pascal, N.: “Long-term assessment of the CALIPSO Imaging Infrared Radiometer (IIR) calibration and stability through simulated and observed comparisons with MODIS/Aqua and SEVIRI/Meteosat”, Atmos. Meas. Tech., 10, 1403-1424, doi:10.5194/amt-10-1403-2017, 2017.
     
  • Garnier, A., Trémas, T., Pelon, J., Lee, K.-P., Nobileau, D., Gross-Colzy, L., Pascal, N., Ferrage, P., and Scott, N. A.: “CALIPSO IIR Version 2 Level 1b calibrated radiances: analysis and reduction of residual biases in the Northern Hemisphere”, Atmos. Meas. Tech., 11, 2485-2500, doi:10.5194/amt-11-2485-2018, 2018.
     

Data Descriptions

In the text below, we provide a brief description of the data fields reported in the IIR Level1B radiances product. The data are grouped in two science data sets: IIR Spacecraft record and Earth Views record, and metadata parameters.

IIR Spacecraft Position, Attitude and Celestial Record


Time_TAI_8.65
Time_TAI_10.6
Time_TAI_12.05
Units: seconds
Format: Float_64

These parameters give the time expressed in International Atomic Time (Temps Atomique International, TAI) in channels 8.65 μm, 10.6 μm and 12.05 μm. Units are in second, starting from January 1, 1993.

Time_UTC_8.65
Time_UTC_10.6
Time_UTC_12.05
Units: UTC - yymmdd.ffffffff
Format: Float_64

These parameters are a replicate of the parameter ‘Time_TAI_xxx’ converted into UTC time and stored in Format: yymmdd.ffffffff in channels 8.65 μm, 10.6 μm and 12.05 μm.

Spacecraft_Position_8.65
Spacecraft_Position_10.6
Spacecraft_Position_12.05
Units: km
Format: Float_64
Valid Range: -8000.0 ... 8000.0
Fill Value: -9999.00

These parameters give the position of the spacecraft in km for the 3 channels 8.65 μm, 10.6 μm and 12.05 μm.

Spacecraft_Velocity_8.65
Spacecraft_Velocity_10.6
Spacecraft_Velocity_12.05
Units: km/sec
Format: Float_64
Valid Range: -8000.0 ... 8000.0
Fill Value: -9999.00

These parameters give the velocity of spacecraft in deg·sec-1 for the 3 channels 8.65 μm, 10.6 μm and 12.05 μm.

Spacecraft_Attitude_8.65
Spacecraft_Attitude_10.6
Spacecraft_Attitude_12.05
Units: degrees
Format: Float_64
Valid Range: -180.0 ... 180.0
Fill Value: -9999.00

These parameters give the attitude of spacecraft in degrees for the 3 channels 8.65 μm, 10.6 μm and 12.05 μm.

Spacecraft_Attitude_Rate_8.65
Spacecraft_Attitude_Rate_10.6
Spacecraft_Attitude_Rate_12.05
Units: deg/sec
Format: Float_64
Valid Range: -10.0 ... 10.0
Fill Value: -9999.00

These parameters give the attitude rate of spacecraft in deg·sec-1 for the 3 channels 8.65 μm, 10.6 μm and 12.05 μm.

Subsatellite_Latitude_8.65
Subsatellite_Latitude_10.6
Subsatellite_Latitude_12.05
Units: degrees
Format: Float_32
Valid Range: -90.0 ... 90.0
Fill Value: -9999.00

These parameters give the sub-satellite latitude in degrees for the 3 channels 8.65 μm, 10.6 μm and 12.05 μm.

Subsatellite_Longitude_8.65
Subsatellite_Longitude_10.6
Subsatellite_Longitude_12.05
Units: degrees
Format: Float_32
Valid Range: -90.0 ... 90.0
Fill Value: -9999.00

These parameters give the sub-satellite longitude in degrees for the 3 channels 8.65 μm, 10.6 μm and 12.05 μm.

Earth View Record


Lidar_Shot_Time
Units: seconds...TAI
Format: Float_64
Valid Range: 4.204E8 ... 1.072E9

This parameter gives the lidar shot time expressed in International Atomic Time (Temps Atomique International, TAI). Units are in second, starting from January 1, 1993.

Lidar_Shot_UTC_Time
Units: UTC - yymmdd.ffffffff
Format: Float_64
Valid Range: 60426.0 ... 261231.0

This parameter is a replicate of the parameter ‘Lidar_Shot_Time’ converted into UTC time and stored in Format: yymmdd.ffffffff.

Latitude
Units: degrees
Format: Float_32
Valid Range: -90.0 ... 90.0
Fill Value: -9999.00

This parameter gives the geodetic latitude at the center of the pixel.

Longitude
Units: degrees
Format: Float_32
Valid Range: -180.0 ... 180.0
Fill Value: -9999.00

This parameter gives the geodetic longitude at the center of the pixel.

Image_Time_8.65
Image_Time_10.6
Image_Time_12.05
Units: seconds...TAI
Format: Float_64
Valid Range: 4.204E8 ... 1.072E9
Fill Value: -9999.0000

These parameters give the IIR image time for channels 8.65 μm, 10.6 μm and 12.05 μm, expressed in International Atomic Time (Temps Atomique International, TAI). Units are in second, starting from January 1, 1993.

Image_UTC_Time_8.65
Image_UTC_Time_10.6
Image_UTC_Time_12.05
Units: UTC - yymmdd.ffffffff
Format: Float_64
Valid Range: 60426.0 ... 261231.0
Fill Value: 921231.88

These parameters are a replicate of the parameter ‘Image_Time_xxx’ converted into UTC time and stored in Format: yymmdd.ffffffff.

Calibrated_Radiances_8.65
Calibrated_Radiances_10.6
Calibrated_Radiances_12.05
Units: Watts per square meter per steradian per micron
Format: Int_16
Raw Data Valid Range: 0 ... 32000
Valid Range: 0 ... 32
Fill Value: -9999
Scale Factor: 1000.00
Offset: 0.00000
Scale Equation: data/scale_factor + offset

These parameters give the calibrated radiances expressed in Wm-2sr-1μm-1 for each pixel in channels 8.65 μm, 10.60 μm and 12.05 μm.

The radiances are regularly calibrated in flight using images of a temperature-monitored warm blackbody source (at about 295 K) and images from cold deep space (about 4K) views. In addition, two distinct sets of correction coefficients were implemented in the Version 2 algorithm: the first set is an equalization correction, which is applied to about half of each individual image with respect to the other part of the image. The second set of coefficients corrects overall radiometric biases that affected the whole image. These correction coefficients are applied at season-dependent latitudes, typically north of 30°N, as a function of the elapsed time since night-to-day transition. The calibrated images are resampled and registered on a 1 km resolution unique grid centered on the lidar ground track.


Viewing_Zenith_Angle_8.65
Viewing_Zenith_Angle_10.6
Viewing_Zenith_Angle_12.05
Units: degrees
Format: Int_16
Valid Range: 0.0 ... 180.0
Fill Value: -9999
Scale Factor: 100.000
Offset: 0.00000
Scale Equation: data/scale_factor + offset
Raw Data Valid Range: 0 ... 18000

These parameters give the viewing zenith angle for each pixel in channel 8.65μm, 10.60 μm, and 12.05 μm.

Viewing_Azimuth_Angle_8.65
Viewing_Azimuth_Angle_10.6
Viewing_Azimuth_Angle_12.05
Units: degrees
Format: Int_16
Valid Range: -180.0 ... 180.0
Fill Value: -9999
Scale Factor: 100.000
Offset: 0.00000
Scale Equation: data/scale_factor + offset
Raw Data Valid Range: -18000 ... 18000

These parameters give the viewing azimuth angle for each pixel in channel 8.65μm, 10.60 μm, and 12.05 μm.

Sequence_Number_8.65
Sequence_Number_10.6
Sequence_Number_12.05
Units: N/A
Format: Int_16
Valid Range: 0 ... 24576
Fill Value: -9999

A sequence is a collection of 6 images: Earth views at 8.65 μm, 10.6 μm and 12.05 μm and calibration views (deep space or blackbody) at 8.65 μm, 10.6 μm and 12.05 μm. These parameters are identifiers of the sequence during the IIR acquisition.

Pixel Quality Index
Units: N/A
Format: UInt_32
Valid Range: 0 ... 15745287

The Pixel Quality Index is an indicator provided for each pixel. It is related to specific steps in the processing and indicates whether a pixel is of good or bad quality.

Bits 1-3 give the overall quality of the pixel for scientific analysis. Bits 4-21 include more detailed information and bits 22-24 indicate if an equalization correction has been applied (Version 2 only).

Bits Description
1 Pixel quality channel 12.05: 0=Good; 1=Bad
2 Pixel quality channel 10.60: 0=Good; 1=Bad
3 Pixel quality channel 08.65: 0=Good; 1=Bad
4-8 If bit 9=0: Number of interpolated pixels in IIR matrix used in Level 1 bi-cubic interpolation (from 0 to 16), channel 12.05
If bit 9=1, then 1: Saturated pixel; 2: Missing pixel
9 Bad pixel, channel 12.05
10-14 If bit 15=0: Number of interpolated pixels in IIR matrix used in Level 1 bi-cubic interpolation (from 0 to 16), channel 10.6
If bit 15=1, then 1: Saturated pixel; 2: Missing pixel
15 Bad pixel, channel 10.6
16-20 If bit 21=0: Number of interpolated pixels in IIR matrix used in Level 1 bi-cubic interpolation (from 0 to 16), channel 08.65
If bit 21=1, then 1: Saturated pixel; 2: Missing pixel
21 Bad pixel, channel 08.65
22 Equalization correction applied, channel 12.05: 0=No; 1=Yes (spare in Version 1)
23 Equalization correction applied, channel 10.60: 0=No; 1=Yes (spare in Version 1)
24 Equalization correction applied, channel 08.65: 0=No; 1=Yes (spare in Version 1)
25-32 Spare

IIR Metadata Record

Product_ID
An 80-byte (max) character string specifying the data product name. The value of this string is "L1_IIR".

Date_Time_at_Granule_Start
A 27-byte character string that reports the date and time at the start of the file orbit segment (i.e., granule). The format is yyyy-mm-ddThh:mm:ss.ffffffZ.

Date_Time_at_Granule_End
A 27-byte character string that reports the date and time at the end of the file orbit segment (i.e., granule). The format is yyyy-mm-ddThh:mm:ss.ffffffZ.

Date_Time_at_Granule_Production
This is a 27-byte character string that defines the date at granule production. The format is yyyy-mm-ddThh:mm:ssZ.

Number_of_IIR_Grid_Line_Records
This parameter gives the number of IIR grid line records.

Initial_Subsatellite_Latitude
This parameter gives the first sub-satellite latitude of the granule in degrees.

Initial_Subsatellite_Longitude
This parameter gives the first sub-satellite longitude of the granule in degrees.

Final_Subsatellite_Latitude
This parameter gives the last sub-satellite latitude of the granule in degrees.

Final_Subsatellite_Longitude
This parameter gives the last sub-satellite longitude of the granule in degrees.

Orbit_Number_at_Granule_Start
This parameter gives the orbit number at the granule start time.

Orbit_Number_at_Granule_End
This parameter gives the orbit number at granule stop time.

Orbit_Number_Change_Time
This parameter gives the time at which the orbit number changes in the granule. The time is expressed in UTC time converted from TAI time and stored in Format: yymmdd.ffffffff.

Path_Number_at_Granule_Start
This parameter gives the path number at granule start time.

Path_Number_at_Granule_End
This parameter gives the path number at granule stop time.

Path_Number_Change_Time
This parameter gives the time at which the path number changes in the granule. The time is expressed in UTC time converted from TAI time and stored in Format: yymmdd.ffffffff.

Ephemeris_Files_Used
This is an 160-byte character that reports a maximum of two ephemeris files used in processing the spacecraft position and velocity.

Attitude_Files_Used
This is an 160-byte character that reports a maximum of two attitude files used in processing the spacecraft attitude and attitude rate.

Level_0_Files_Used
This parameter gives the name of the level 0 files used.

Level_1_code_version_Used
This parameter gives the level 1 code version used to process the granule.

Input_parameter_version_number_used_Radiometry
This parameter gives the version number of the calibration module.

Input_parameter_date_of_application_Radiometry
This parameter gives the date at which the calibration module was applied in Format: yyyy-mm-ddThh:mm:ss.ffffffZ.

Input_parameter_version_number_used_Geometry
This parameter gives the version number of the geometry module.

Input_parameter_date_of_application_Geometry
This parameter gives the date at which the geometry module was applied in Format: yyyy-mm-ddThh:mm:ss.ffffffZ.

Percentage_of_8.65_Good_Pixels
Percentage_of_12.05_Good_Pixels
Percentage_of_10.6_Good_Pixels
These parameters give the percentage of good pixels for the channel 8.65 μm, 12.05 μm and 10.6 μm.

Percentage_of_Good_Pixels_3_Channels
This parameter gives the percentage of good pixels for the 3 channels.

Percentage_of_Missing_Pixels
This parameter gives the percentage of missing pixels.

Number_of_Images_Processed
This parameter gives the number of images processed.

Percentage_of_Missing_Images
This parameter gives the percentage of missing images.

Number_of_Equalization_mode
This parameter gives the number of equalization mode.

Altitude_of_Projection
This parameter gives the altitude of projection in km.

Initial_Absolute_Sequence
This parameter gives the smallest sequence number at granule start.

Final_Absolute_Sequence
This parameter gives the largest sequence number at granule end.

Grid_Line_Delta_Time
This parameter gives the time difference between two successive grid lines, in seconds.

Scale_Factor_for_Radiance
This parameter gives the scale factor used to report the calibrated radiances.

Radiance_Offset
This parameter gives the offset used to report the calibrated radiances.

Scale_Factor_for_Viewing_Angle
This parameter gives the scale factor used to report the viewing angles.

Viewing_Angle_Offset
This parameter gives the offset used to report the viewing angles.


NASA
Last Updated: November 22, 2021
Curator: Charles R. Trepte
NASA Official: Charles R. Trepte

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