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LITE Data Processing

The LITE high-rate telemetry data were transferred from the orbiter to the LITE operations center at Johnson Space Flight Center (JSC) and stored on optical platters in a PC format. After the mission was complete, the LITE data on the PC media were delivered to NASA LaRC for archive and post-processing.

A Sun computer utilizing the UNIX operating system was used for the LITE data processing. The processing steps are defined as follows:

Error check the LITE high-rate telemetry data and correct the data when possible.
Transfer the data from the PC media to an optical disk library.
Create the LITE Level 0 data product: Convert the LITE telemetry data from its native form to a computer-compatible format.
Create the LITE level 1 data product.

LITE Level 0 Data Processing Steps:

Decommutate the LITE high-rate telemetry data.
Identify which telemetry frames contain ISDB and QLSD data
Time-tag and synchronize ISDB status parameters with lidar profiles.
Merge temperature and pressure profiles from the NMC data.
Altitude register and geolocate lidar profiles.
Archive the Level 0 data product at the NASA Langley Research Center, Aerosol Research Branch, Hampton, VA 23681.

LITE Level 1 Data Processing Steps:

Correct the profiles for instrument artifacts (two step process).

First, a fixed baseline correction was performed for every lidar profile.
Second, correct for low-level, random phase oscillations found in the low-gain data.

Subtract the DC offset from each lidar profile. Two methods were used depending on the lidar configuration.

Slope Method: the offset value was calculated by matching the slope of the backscatter profile to the slope of a reference (density) profile over two high altitude regions.
Averaged Signal Method: The offset value was determined by averaging the signal over a single high altitude region.

Method Daytime Nighttime

Slope . High-gain 355 and 532 nm

Averaged Signal 355, 532, and 1064 nm 1064 nm and Low-gain 355 and 532 nm

Reference profiles to a constant altitude grid. Interpolate the lidar profiles to a geolocated, common altitude grid, which extends from -4.985 to 40.0 km with a 15 m vertical resolution.

Determine LITE system calibration constants for the 355 nm and 532 nm wavelength profiles and report them for each lidar profile.
The Level 1 System Calibration Document describes how the LITE system calibration constants were determined, discusses the variability in the system constants, and the applications of the LITE system calibration constants.