Aquarius Level 0-to-1A Processing Rule #1: save everything from the Level 0 data. Rule #2: never forget Rule #1! The objective is to ensure that the Level

Aquarius Level 0-to-1A Processing

• Rule #1: save everything from the Level 0 data.• Rule #2: never forget Rule #1!• The objective is to ensure that the Level 0-to-1A

conversion is fully reversible.

Level-0 File Overview

• A single copy of the contents Aquarius memory at the time of the downlink, in time order, as generated by the Aquarius preprocessor.

• Data consist of binary science blocks spanning a period of ~14 hours (110 Mbytes).

Science Block Structure

FORMAT OF THE AQUARIUS SCIENCE BLOCK10/21/05

NOTES:- All multi-byte values are big-endian; MSB first, and MS-bit (bit N-1 for a word of N bits) is first- Telemetry Item (or packet) definitions, referenced in the Type column, are contained in the Telemetry Dictionary- The Telemetry Item packets, e.g. Antenna Telemetry Item, are defined in the telemetry dictionary, and their sizes in this table must be kept current with the definitions there.

Section Field or Group Type Size (bytes) Byte Offset Definition/Notessync word integer 4 0 constant: 0xdeadbeefGPS time tag integer 4 4 TAI, Epoch Jan 1 1980, midnighttime tag offset integer 4 8 Units of 10usec, range: [0-100000]antenna telemetry Antenna Telemetry Item 5 12ICDS processing status ICDS Processing Status Item 11 17ICDS engineering telem ICDS Engineering Item 20 28mechanical telemetry Mechanical Thermal Item 71 48ADPU telemetry ADPU Telemetry Item 6 119ATC telemetry ATC Telemetry Item 45 125 One channel of ATC telemetryscatterometer HKT Scatterometer Telemetry Item 39 170 Scatterometer housekeepingscatterometer science data Scatterometer Block 336 209 See “block” worksheet.

radiometer science data Radiometer Block 1982 545See “block” worksheet. This includes radiometer telemetry

Footer checksum integer 2 2527

SCI BLOCK SIZE: 2529 2529

Header

Science Data

Radiometer Block Item #

field subcycle #

# of bits ea.

# of ch

total # of bits

Radiometer:1 Header 16 1 162 telemetry (1/4 of frame) 400 1 4003 Radiometer Status 80 80

Subcycle #14 SAvg1 1 16 12 1925 SAvg2 1 16 12 1926 SAvg3 1 16 12 1927 SAvg4 1 16 12 1928 SAvg5 1 16 12 1929 SAvg6 1 16 12 192












Long' Accumulations:76 LAvg1 1-10 16 12 19277 LAvg2 1-10 16 12 19278 LAvg3 1-10 16 12 19279 LAvg4 1-10 16 12 19280 LAvg5 11-12 16 12 19281 LAvg6 11-12 16 12 19282 LAvg7 11-12 16 12 19283 LAvg8 11-12 16 12 192

Rad Totals: # bits 15856# bytes 1982

Scatterometer Blockfield subcycle # # of bits ea. total # of bits

and so forthB3VH pwr 7 16 16B3nH pwr 7 16 16B3HH pwr 7 16 16subcycle header 8 8 8B1HV pwr 8 16 16B1nV pwr 8 16 16B1VV pwr 8 16 16B1VH pwr 8 16 16B1nH pwr 8 16 16B1HH pwr 8 16 16B2HV pwr 8 16 16B2nV pwr 8 16 16B2VV pwr 8 16 16B2VH pwr 8 16 16B2nH pwr 8 16 16B2HH pwr 8 16 16B3HV pwr 8 16 16B3nV pwr 8 16 16B3VV pwr 8 16 16B3VH pwr 8 16 16B3nH pwr 8 16 16B3HH pwr 8 16 16Loopback measurementsB1HV pwr 1-8 16 16B1nV pwr 1-8 16 16B1VV pwr 1-8 16 16B1VH pwr 1-8 16 16B1nH pwr 1-8 16 16B1HH pwr 1-8 16 16B2HV pwr 1-8 16 16B2nV pwr 1-8 16 16B2VV pwr 1-8 16 16B2VH pwr 1-8 16 16B2nH pwr 1-8 16 16B2HH pwr 1-8 16 16B3HV pwr 1-8 16 16B3nV pwr 1-8 16 16B3VV pwr 1-8 16 16B3VH pwr 1-8 16 16B3nH pwr 1-8 16 16B3HH pwr 1-8 16 16B1HV DC 1-8 16 16B1NV DC 1-8 16 16scat telem 312

field subcycle # # of bits ea. total # of bitssubcycle header 1 8 8

B1HV pwr 1 16 16B1nV pwr 1 16 16B1VV pwr 1 16 16B1VH pwr 1 16 16B1nH pwr 1 16 16B1HH pwr 1 16 16B2HV pwr 1 16 16B2nV pwr 1 16 16B2VV pwr 1 16 16B2VH pwr 1 16 16B2nH pwr 1 16 16B2HH pwr 1 16 16B3HV pwr 1 16 16B3nV pwr 1 16 16B3VV pwr 1 16 16B3VH pwr 1 16 16B3nH pwr 1 16 16B3HH pwr 1 16 16subcycle header 2 8 8B1HV pwr 2 16 16B1nV pwr 2 16 16B1VV pwr 2 16 16B1VH pwr 2 16 16B1nH pwr 2 16 16B1HH pwr 2 16 16B2HV pwr 2 16 16B2nV pwr 2 16 16B2VV pwr 2 16 16B2VH pwr 2 16 16B2nH pwr 2 16 16B2HH pwr 2 16 16B3HV pwr 2 16 16B3nV pwr 2 16 16B3VV pwr 2 16 16B3VH pwr 2 16 16B3nH pwr 2 16 16B3HH pwr 2 16 16subcycle header 3 8 8B1HV pwr 3 16 16B1nV pwr 3 16 16B1VV pwr 3 16 16and so forth

Level-1A Product Overview

• Level-1A data consists of unpacked, unconverted science data and instrument housekeeping telemetry, with navigation and required spacecraft telemetry.

• Each file contains 1 orbit (starting at South Pole crossing) plus 10 minutes at each end.

• Level-1A products are formatted using HDF5:– Machine-independent, hierarchical, self describing format– Attributes contain descriptive information about the entire file or

individual objects within the file– Groups provide logical association and hierarchy– Data objects are multidimensional arrays of standards types

Level-1A Product Elements

• Product metadata, i.e., descriptive information about the entire file (e.g., sensor, time, quality)

• Data characteristics (number of blocks, etc.)• Science block metadata (time and quality)• Raw sensor data:

– Block header elements– Housekeeping telemetry by subsystem– Radiometer and scatterometer science data,

• Navigation data (original sampling rate)– Orbit vectors from predicted or definitive ephemeris– Attitude data from SAC-D telemetry

• Unpacked and converted Aquarius housekeeping telemetry• SAC-D housekeeping telemetry (selected fields converted)

Level 0-to-1A Mapping

Time tag offset

GPS time tag

Synch word

Antenna telemetry

ICDS processing status

ICDS engineering telemetry

APDU telemetry

Mechanical telemetry

ATC telemetry

Scatterometer HKT

Scatterometer science data

Radiometer NRT HKT

Radiometer RT HKT

Radiometer science data

Checksum

Synch and Time Tag

Aquarius Raw Telemetry

Scatterometer science dataHeaderPower

LoopbackDC

Radiometer science dataHeader

Short AccumulationsLong Accumulations

Level-1A Ancillary Data

• Orbit ephemeris data provided by CONAE:– Predictive ephemeris for near-real-time processing– Definitive ephemeris for refined processing– GPS data from SAC-D as backup

• Attitude data from SAC-D housekeeping telemetry• Additional SAC-D housekeeping telemetry provided by

CONAE from downlink data

Calibration and Orbit Adjust Data

• Cold sky calibration and orbit adjust periods will be identified during Level-1A processing, either from the command schedule or the spacecraft housekeeping telemetry.

• Data from these periods (plus additional data as needed for stabilization, TBD) will be written to separate files and excluded from downstream processing.

• Calibration files will be provided for offline analysis.

Level-1A Format Examples

3.1 Mission and Documentation

Product Name (character): the name of the product file (without path).Title (character): "Aquarius Level‑1A Data".Data Center (character): "NASA/GSFC Aquarius Data Processing Center". Mission (character): "SAC-D Aquarius".Mission Characteristics (character): "Nominal orbit: inclination = 98.0 (Sun-synchronous); node = 6

PM (ascending); eccentricity = <0.002; altitude = 650 km; ground speed = 6.825 km/sec".Sensor (character): "Aquarius".Data Type (character): "SCI”, “CAL” or “DMP”.Software ID (character): identifies version of the operational software used to create this product.Processing Time (character): local time of generation of this product; concatenated digits for year,

day-of-year, hours, minutes, seconds, and fraction of seconds in the format of YYYYDDDHHMMSSFFF.

Input Files (character): the name of the Level‑0 file(s) (without path) from which the current product was created. This information is stored in the product as part of its processing history.

Processing Control (character): all input and processing control parameters used by the calling program to generate the product. Vertical bars or carriage return characters serve as parameter information delimiters. This information is stored in the product as part of its processing history.

Level-1A Format Examples (cont.)

4.2.3 Raw Radiometer Science Data

radiom_header (2‑byte integer, array size Number of Blocks): long_name = ”Radiometer block header"; this header specifies the packet type (standard or memory dump) and the housekeeping telemetry packet number (0 through 3).

radiom_savg (2‑byte integer, array size Number of Blocks x Radiometer Subcycles x Radiometer Short Accumulations x Radiometer Channels): long_name = “Radiometer Short Accumulations”; radiometer data accumulated and averaged within a subcycle.

radiom_lavg (2‑byte integer, array size Number of Blocks x Radiometer Long Accumulations x Radiometer Channels): long_name = “Radiometer Long Accumulations”; radiometer data accumulated and averaged over multiple subcycles within a block.

4.2.4 Raw Scatterometer Science Data

scatter_headers (byte, array size Number of Blocks x Scatterometer Subcycles): long_name = “Scatterometer subcycle headers”; headers for each scatterometer subcycle within a block.

scatter_pwr (2‑byte integer, array size Number of Blocks x Scatterometer Subcycles x Scatterometer Channels): long_name = “Scatterometer Power”; raw scatterometer power data for each subcycle within a block.

scatter_loop (2‑byte integer, array size Number of Blocks x Scatterometer Channels): long_name = “Scatterometer Loopback Measurements”; scatterometer loopback data average over the subcycles within a block.

scatter_dc (2‑byte integer, array size Number of Blocks x 2): long_name = “Scatterometer DC data”; raw scatterometer DC data averaged over the subcycles within a block.

Aquarius Telemetry ExampleMnemonic(*) Description Units Range Rn_CNDNDT CND ND Temp °C Rn_VNDTP Vert ND Temp+ °C Rn_VNDTN Vert ND Temp - °C Rn_HNDTP Horiz ND Temp+ °C Rn_HNDTN Horiz ND Temp - °C Rn_VDL1TP Vert Dicke Load 1 Temp+ °C Rn_VDL1TN Vert Dicke Load 1 Temp - °C Rn_HDL1TP Horiz Dicke Load 1 Tem p+ °C Rn_HDL1TN Horiz Dicke Load 1 Temp - °C Rn_VDL2T Vert Dicke Load 2 Temp °C Rn_HDL2T Horiz Dicke Load 2 Temp °C Rn_VLNAT Vert LNA Temp °C Rn_HLNAT Horiz LNA Temp °C Rn_CBPT RFE Cntl Bd Pwr Temp °C Rn_CBT RFE Cntl Bd Temp °C Rn_CNDI CND Current Amps Rn_HNDI HND Current Amps Rn_VNDI VND Current Amps

Aquarius Level-1A Merge

• Multiple versions of Level-1A products will be generated for each orbit from overlapping periods in successive Level-0 files.

• Level-1A merge processing will consolidate these into a single product by selecting the best quality data for each science block using TBD metrics.

Aquarius Level-1B Products

• Separate files for radiometer and scatterometer.• Formatted using HDF5• Product-level metadata is essentially the same as for

Level 1A.• Calibrated science data, processing information and

quality indicators as defined for each data type, per beam and polarization.

• Navigation and geolocation data at block or subcycle times.

Radiometer Level-1B Science Data

• Calibrated brightness temperatures (per subcycle)• Noise temperatures (per block)• Voltage offsets (per block)• Gains (per block)• RFI flags (per subcycle)• Brightness temperatures RMS (per subcycle)

Scatterometer Level-1B Science Data

• Sigma0 (backscatter)

• KPC (normalized standard deviation)• Signal-to-noise ratio• Noise value

All fields generated per subcycle

Level-1B Navigation Data

• Orbit position and velocity (per block)• Attitude roll, pitch and yaw angles (per block)• Beam center latitude/longitude (per beam and subcycle)• Beam edge latitude/longitude (ellipse major and minor

axes) (per beam and block)• Incidence and azimuth angles (per beam and block)• Polarization roll (per beam and block)• Doppler shift (per beam and block)

Pointing Knowledge Assessment

• Pointing knowledge requirement is 0.1 degree 3 sigma, driven primarily by the radiometer sensitivity to the incidence angle.

• This is equivalent to about 2 km of location accuracy at the surface.

• Verifying this level of accuracy could be challenging with the Aquarius beam size.

• Overlap with land surfaces should be useful, but approach needs to be developed.

• This will most likely be performed as a separate processing step after Level-1B processing.

Pointing Knowledge Assessment (cont.)

• What is the expected sensitivity of the radiometer signal to land vs. ocean surface?

• How does this vary with surface type?• Is surface elevation a factor?• How is polarization affected?• Will the sensitivity and coverage be sufficient to characterize

systematic as well as static errors?• How can the method be designed to process a reasonable minimum

subset of the radiometer data (60,000 blocks, 720,000 subcycles) per day?

• Does the scatterometer provide an independent assessment?

Documents

Aquarius Level 0-to-1A Processing Rule #1: save everything from the Level 0 data. Rule #2: never forget Rule #1! The objective is to ensure that the Level