LITE Raw, High-rate Telemetry Data
The LITE high-rate telemetry data consists of a stream of packed binary data
blocks, or major frames. Each major frame has locations for:
- The full-resolution digitized lidar signals for the 355 nm, 532 nm, and 1064 nm wavelengths,
- ISDB (Instrument Status Data Block) data, and
- QLSD (Quick Look Science Data).
Description of LITE Operations
- After a lidar return profile is digitized:
- The lidar profiles at each of 3 wavelengths are output to a major frame.
- The status information (ephemeris, timing, and engineering data related to the health, status, and configuration of the instrument)
are written to storage buffers.
- After every ten lidar pulses (one second cycle), the data in storage buffers are reorganized into an ISDB.
- An ISDB is transferred to a major frame one to five lidar pulses later.
- Every ten seconds (100 lidar pulses), a 100-pulse average of lidar profiles for the 355 nm and 532 nm wavelengths is performed and
stored into a QLSD buffer.
- The contents of the QLSD buffer are output to ten consecutive major frames.
- The major frame that contains the first QLSD information ALWAYS follows the major frame for the last lidar pulse in the average.
- The last lidar pulse in a 100-second average is ALWAYS the tenth lidar pulse in a one second cycle.
- The first ISDB that appears after the major frame for this last lidar pulse contains the status information for that one second cycle.
- The remaining one second cycle profiles from the 100-second average can now be synchronized with an ISDB.
- In the level 0 and level 1 data product, if an ISDB is missing due to gaps in telemetry data, previously stored ISDB
information was used in substitute. The lidar profiles
with repeated ISDB information were flagged. Thus no lidar profiles were eliminated from the level 0 or level 1 data product.
LITE Major Frame Description
The following grid shows the byte locations, and the LITE data organization. Each major frame contains 50 minor frames.
- The lidar profile for 355 nm contains 5500 12-bit digitized signals, 8250 bytes.
- The lidar profile for 532 nm contains 5500 12-bit digitized signals, 8250 bytes.
- The lidar profile for 1064 nm contains 4040 12-bit digitized signals, 6060 bytes.
- An ISDB block contains 768 bytes.
- A Quick-Look Science Data (QLSD) block contains 1194 bytes.
- The SYNC data are the first 8 bytes (64 bits) of each minor frame.
- The first 48 bits contain the SYNC pattern.
- The next 16 bits contain the minor frame counter.
- SYNC Pattern (HEX): faf33403cd40 and 00XX.
- Byte 41 (bits 321-328) in the first major frame contains the ISDB and QLSD flags.
- Bit 321 - QLSD flag. If QLSD flag = 1, then major frame contains a QLSD block.
- Bit 323 - ISDB flag. If ISDB flag = 1, then major frame contains an ISDB block.
