NEODAAS

HRPT File Format

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HRPT Format

Note the bit numbering is MSB=bit 1, LSB=bit 10 in this document.

A complete description (for the KLM satellites) can be found in the NOAA documentation.

One scanline of HRPT data contains one minor frame (11090 10-bit words). The minor frame number is contained in word 7. There are three minor frames, numbered 1, 2 and 3, per major frame.

TIP data

The TIP block (520 words) contains 5 TIP minor frames of 104 words each. Each two-byte word contains one 10-bit TIP word, of which bits 1 to 8 contain TIP data, the other two being parity. The bits numbered "1" to "8" are actually stored in the word as bits 9 to 2, with bits 1 and 0 used for parity. Thus there are 104 bytes of data in a TIP minor frame. See page 4-40 (table 4-14). TIP major frame count is word 3 bits 4 to 6, ie. ((words[3] & 0x70) >> 4). TIP minor frame number is TIP word 4 bit 8 and TIP word 5 bits 1 to 8, ie. (words[5] >> 2) + ((words[4] & 4) << 6). TIP analogue channel number is TIP word 3 bits 7,8 and word 4 bits 1 to 7, ie. ((words[3] & 0xC) << 5) + ((words[4] & 0x3F8) >> 3).

Analogue data is described in table 15-14 on page 15-47.

CPU-A data, see page 15-83, table 15-15, consists of 135 16-bit words, divided into 9 sub-tables of 15 words each, eg. Altitude is word 13 of table 4. The sub-tables are read out in the order 1, 2, 1, 3, 1, 4, ..., 1, 9, repeat. A full read out is thus 16 sub-tables = 16*15 = 240 words. As only 6 bytes are available in each TIP Minor Frame then each minor frame contains 3 words of CPU data. 5 minor frames will contain 15 words, ie. one sub-table can be stored in one scan line. So the complete CPU data needs 16 lines. TIP data is repeated for three lines though (or only transmitted in HRPT minor frame 1 for KLM) so the full read out needs 16*3 = 48 lines.

Note about synchronisation: words 1, 2 and 3 of each sub-table will be kept together in a minor frame (rather than 2, 3 and 4 for example). Word 1 of sub-table 1 is not necessarily in minor frame 0 though. Word 1 of sub-table 1 can be found by looking for words 14 and 15 of sub-table 9 as they will always contain 0xEB90 and 0x146F (60309 and 5231).

Attitude on pre-N14: Yaw,Roll,Pitch are table 1, words 13,14,15; scaling factor 8192. Altitude is table 4, word 4.

References: Programming and Control Handbook for Advanced TIROS-N Spacecraft Series (NOAA-E,F,G)

1. Volume 1, 4-40 (TIP minor frame format)
2. Volume 1, 5-56 (How to read TIP telemetry)
3. Volume 1, 5-71 (CPU telemetry)
4. Volume 2, 15-48 (Analogue telemetry table)
5. Volume 2, 15-83 (CPU telemetry table)

NOAA KLM-series (NOAA-15, 16, 17)

Word 7, bit 10 indicates which channel 3A or 3B is operating (note that this is not a reliable indicator to check on pre-N15 satellites).

Visible channels 1, 2 and 3A have dual calibration slopes.

HRPT Minor frame 1 is the only one to contain TIP data (2 is spare and 3 is for AMSU data).

DartCom HRPT Format

DartCom format only keeps the sixth of the first six framesync words, and 23 of the last 100 aux sync words but otherwise is standard HRPT. BURL similarly drop words, keeping only the fifth and sixth of the first six framesync words, 21 of the middle 127 spare words, and none of the last 100 aux sync words.

Quorum HRPT Format

Quorum HRPT format is simply standard HRPT format (ie. unpacked into 11090 16-bit words). Four pseudo-frames are defined to hold extra information about the data. All pseudo frames start with a word 0x8000 followed by a word describing the frame contents:

• 0x8000 - frame contains NORAD two-line orbital elements
• 0x8100 - frame contains data start time
• 0x8200 - frame contains resync time
• 0x8300 - frame contains data end time

The file always contains an elements frame followed by a start time frame, then HRPT frames with resync frames possibly interspersed, and finally an end time frame. Times are stored as unix 32-bit seconds since 1970, with the most significant two bytes in the third word of the frame and the least significant two in the fourth word of the frame.

Feng-Yun 1 format

Each HRPT line is twice the size of NOAA HRPT since there are ten channels instead of five, ie. 22180 words stored on disk 44360 bytes. The time code has no day and the spacecraft identifier is in the bottom four bits instead. The MVISR image data offset is 1600 instead of 750.

SeaWiFS HRPT Format

Note that SeaWiFS data is supplied in level-0 or level-1 format. The following description refers only to the format received from the spacecraft prior to conversion to level-0. This raw format is not stored anywhere.

SeaWiFS Level-0 Format

Also known as NASA Frame Formatter format, this is the format used for storage of raw SeaWiFS data, as input to the level-1 conversion software. Words are stored in big-endian form. Note: the following tables used byte offsets not word offsets.

Header, 512 bytes

Record, 21504 bytes (21KB)

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