GB/T 33996-2017Hierarchy and nomenclature of lunar exploration data products (English PDF)

2.1 Lunar exploration

Observation and sampling research activities on the material composition, surface features, physical fields, internal structure, and origin and evolutionary history of the Moon, carried out by means of lunar-orbiting or landing probes.

[GB/T 30114.1-2013, definition 3.1.1]

2.2 Data product

Digital information provided for user applications, obtained by the effective use of data analysis methods to extract information of value to the user from massive raw information, and presented in an intuitive and effective form.

[GB/T 30114.1-2013, definition 4.32]

2.3 Packet data

Application-oriented, protocol-based standard data units generated by the scientific instruments.

Note: includes packet protocol data units and bitstream protocol data units.

2.4 Calibration

Process of determining the quantitative relationship between the measurement data of an instrument and the actual physical quantity, using known information of determined value by means of comparison, adjustment, correction and similar methods.

Note: common calibrations include radiometric calibration, energy spectrum calibration and geometric calibration.

[GB/T 30114.1-2013, definition 4.37]

2.5 Radiometric correction

Correction of systematic and random radiometric distortion or deformation produced by external factors and by the data acquisition and transmission system.

[GB/T 14950-2009, definition 5.195]

2.6 Selenometric positioning

Determination of the position on the lunar surface of each sampling point of a sensor, and of other related geometric parameters, from the ephemeris parameters, attitude parameters and sensor parameters of the probe, taking into account the rotation and shape of the Moon, by transformation between the coordinate systems.

2.7 Coordinated universal time (UTC)

Time scale maintained by the International Bureau of Weights and Measures (BIPM) and the International Earth Rotation Service (IERS), which is the basis for the coordinated dissemination of standard frequencies and time signals.

Note 1: This definition is taken from Recommendation ITU TF.686 of the International Telecommunication Union - Radiocommunication Sector (ITU-R). ITU-R also specifies UTC as the abbreviation of coordinated universal time.

Note 2: Coordinated universal time is often (inaccurately) called Greenwich Mean Time (GMT).

Note 3: Further information is available at the following addresses: International Telecommunication Union: http://www.itu.int/itudoc/itu-r/rec/tf/index.html; International Bureau of Weights and Measures: http://www.bipm.fr; International Earth Rotation Service: http://www.iers.org/

[GB/T 7408-2005, definition 3.1]

3.1 General

According to the function of the data products and the users they are intended for, the processing of lunar exploration data products is divided into stages. Data products are divided into 3 levels, from lowest to highest: level 0, level 1 and level 2 data products.

3.2 Level 0 data products

Level 0 data products are the packet data and the instrument acquisition data formed after the data downlinked from the probe have been processed on the ground by demodulation, frame synchronisation, descrambling, channel decoding, depacketisation, decompression and similar operations. They are data acquired by the scientific instruments that have not been calibrated or selenometrically positioned. Level 0 data products are further divided into two sub-levels, level 0A and level 0B, described in Table 1.

Table 1 - Hierarchy of level 0 data products:

Level 0A data products (Level 0A): packet data of each scientific instrument for a single ground receiving station, formed after the data downlinked from the probe have been processed on the ground by demodulation, frame synchronisation, descrambling, channel decoding, demultiplexing and similar operations.

Level 0B data products (Level 0B): data acquired by each scientific instrument, formed from level 0A data by merging the data of several ground receiving stations (where applicable), sorting and removing duplicates to form packet data, and then removing the packet structure and decompressing (where applicable).

3.3 Level 1 data products

Level 1 data products are data obtained from level 0B data products by numerical conversion of instrument parameters such as temperature, voltage and current, and reorganised by observation period.

Note: for a lunar orbiter, one orbit is taken as one observation period; for a lander performing in-situ exploration, one Earth day or one data transmission arc is taken as one observation period; for a rover, the period from the start of one observation point to the start of the next (including the movement of the rover and the observation process at the point) is taken as one observation period.

3.4 Level 2 data products

Level 2 data products are data obtained from level 1 data products by correction using the calibration results, and provided with geometric information.

Level 2 data products are divided into two sub-levels, level 2A and level 2B, described in Table 2.

Table 2 - Hierarchy of level 2 data products:

Level 2A data products (Level 2A): products derived from level 1 data by correction using the calibration results, such as radiometrically corrected products.

Level 2B data products (Level 2B): products derived from level 2A data and provided with selenometric positioning information.

4.1 General

4.1.1

A data product file name consists of 10 elements, in the following order: mission identifier, receiving station identifier, instrument identifier, data product type, data time characteristic, start time, end time, observation period number (or data transmission task number), product version number and product level. The first 9 elements are separated by underscores.

4.1.2

Latin letters in the file name are in upper case.

4.1.3

The format of a data product file name is CEx_st_pl_ty_dc_yyyymmddhhmiss_YYYYMMDDHHMISS_ob_ver.lv. The definitions and rules for each element are given in 4.2 to 4.11. Examples of data product file names are given in Annex A.

4.2 Mission identifier

The mission identifier begins with CE; x is the mission number, expressed as a digit, 1 character long. It may be followed, separated by a hyphen, by a probe identifier, which is an upper-case letter abbreviation 1 character long.

4.3 Receiving station identifier

st is the receiving station identifier, 4 characters long, indicating the ground receiving station of the data, as an English abbreviation.

4.4 Instrument identifier

pl is the abbreviation of the scientific instrument. It may be followed, each separated by a hyphen, by the operating mode identifier w and the observation data number XXXX. The operating mode is expressed as a letter or digit, 1 character long. The observation data number is the number given to data divided up (for example into scenes or frames) by the instrument within the same observation period and operating mode; it is expressed in digits, 4 characters long, padded with leading zeros where shorter.

4.5 Data product type

ty is the data product type identifier, 3 characters long, with the following meanings:

a) SCI - science data;

b) TTC - engineering telemetry data;

c) ENG - instrument engineering data;

d) AUX - auxiliary data;

e) ATT - attitude data;

f) EPH - orbit (ephemeris) data;

g) QLY - quality data;

h) CAL - calibration data.

4.6 Data time characteristic

dc is the data time characteristic identifier, 1 character long, with the following values:

a) R - real-time data (data downlinked directly after acquisition);

b) P - playback data (data stored on the probe and played back with a delay);

c) N - containing both real-time data and playback data.

4.7 Start time

yyyymmddhhmiss is the time of the first frame of data in the file, in coordinated universal time (UTC), where yyyy is the year, 4 characters long, and mm the month, dd the day, hh the hour, mi the minute and ss the second, each 2 characters long; values that are shorter are padded with leading zeros.

4.8 End time

YYYYMMDDHHMISS is the time of the last frame of data in the file, in coordinated universal time (UTC), where YYYY is the year, 4 characters long, and MM the month, DD the day, HH the hour, MI the minute and SS the second, each 2 characters long; values that are shorter are padded with leading zeros.

4.9 Observation period / data transmission task number

For level 0 data products, ob is the data transmission task number, 4 characters long, padded with leading zeros where shorter.

For level 1 and level 2 data products, ob is the observation period number, 4 characters long, padded with leading zeros where shorter.

4.10 Product version number

ver is the product version, 1 character long, taking the values A to Z: the first version is A, the second B, and so on.

4.11 Product level

lv is the product level, 2 characters long, with the following values:

a) 0A - level 0A data product;

b) 0B - level 0B data product;

c) 01 - level 1 data product;

d) 2A - level 2A data product;

e) 2B - level 2B data product.