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.
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).
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.,
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
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
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.
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.
Units: Watts per square meter per steradian per micron
Raw Data Valid Range: 0 ... 32000
Valid Range: 0 ... 32
Fill Value: -9999
Scale Factor: 1000.00
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.
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.
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
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).
Pixel quality channel 12.05: 0=Good; 1=Bad
Pixel quality channel 10.60: 0=Good; 1=Bad
Pixel quality channel 08.65: 0=Good; 1=Bad
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
Bad pixel, channel 12.05
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
Bad pixel, channel 10.6
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
Bad pixel, channel 08.65
Equalization correction applied, channel 12.05: 0=No; 1=Yes (spare in Version 1)
Equalization correction applied, channel 10.60: 0=No; 1=Yes (spare in Version 1)
Equalization correction applied, channel 08.65: 0=No; 1=Yes (spare in Version 1)