MET Light Detection and Ranging (LIDAR) data sets

Data Set Overview

The Phoenix Mars Lander arrived at 68.2184N, 234.2487E on May 25, 2008.

The PHX Atmospheric Lidar Profiles product contains unprocessed (i.e. Digital Numbers not converted to counts or voltage) laser scattering atmospheric profiles. Each operation of the lidar instrument is provided as a separate product, and often more than one operation was conducted per sol.

The EDR Data are organized into Photon Counting (532nm), Analog (532 & 1064nm) and Supplemental (Laser Power, Lidar Background Skylight and sensorhead temperatures).

The lidar instrument is highly configurable, leading to a myriad of possible data volume outcomes. Briefly, a single (vertical) profile of atmospheric scattering is given for a single point in time, and listed as values at various ranges (distance) from the lander (with the difference between successive ranges defining the sampling range interval). Successive profiles, marked with a separate time, determine the temporal sampling interval (period duration), and the total duration is defined as the product of total number of profiles and sampling interval (temporal integration duration). The range sampling interval for analog and photon counting channels can be configured separately,

Supplemental data contains the unprocessed average, min and max laser voltages (provided as an estimate of laser power); inter_pulse analog background values; and sensor-head temperature estimates, as an indicator of co-alignment between laser transmitter and receiver. [WHITEWAY2008]

The Data is organized by a unique identifier (Token) is keeping with the other Phoenix instruments. The token for the Lidar was set each instance of operation, and is provided as a 4 byte hex value.

Every record is stored with both the spacecraft time, and UTC start time, and each data record can thus be retrieved from each table using time as a common key.

Parameters

Each EDR file contains time as the MET Frame count since instrument power on (1 count is 0.01 sec). The range that scattering occurs at is given from the lander deck (approximately vertical) in meters.

EDR files contain 32bit DN for the number of photon counts (532nm photon counting channel) or the average voltage for the analog channels (532 & 1064nm). Supplemental values of the min, max and average laser intensities are provided as 16 bit values; as are the analog background (skylight) values sampled between laser pulses (avg, min, max); and the sensorhead temperatures.

The number of profiles and integration duration are also provided for reference.

During surface operations, the range resolution was nominally set to 20m and 50m, respectively, for the analog and photon counting data; The sampling period was between 1.28 - 20.48 sec, with the vast majority of lidar operations employing 20.24 sec resolution; each operation of the lidar was between 5 and 90 min in total duration, with the average operation lasting 20 min.

Processing

The EDRs are essentially identical to the telemetry messages sent from the MET-Lidar instrument to the Lander computer, converted to ASCII and with the addition of a Lander timestamp (there is no onboard MET clock, so the instrument relies on an internal Frame Count. Matching of this frame count and the Lander clock are made using the MET GDS)

Finally, the data were converted to PDS format, converting the tab-delimited fields to fixed-width fields, and exchanging the multiple packet headers for a single session header by the MET GDS.

Data

All of the data in this data set are contained in ASCII tabular files with detached PDS labels. Data is stored in a separate directory relating to the sol in which the recording of data commenced (i.e. data acquired from 003 10:00 local to 004 10:15 will be in the sol 3 directory)

Individual filenames are constructed as follows:

MS002ELP_00896227243_10CCM0.LBL
1	The first character will always be an 'M', representing MET data.
2	The second character will be an 'S', signifying surface data (versus 'C' for Cruise)
3-5	The next three characters provide the sol number of the data file.
6-8	The next three characters describe the type of MET data, ELP - EDR Lidar Photon Counting *532 nm) ELA - EDR Lidar Analog (532 & 1064 nm) ELS - EDR Lidar Supplemental Data RLP - RDR Lidar Photon Counting *532 nm) RLA - RDR Lidar Analog (532 & 1064 nm) RLS - RDR Lidar Supplemental Data
9	Blank
10-20	SCLK - Spacecraft clock
21	Blank
22-25	Operations Token
26	Producer (M for MET Team)
27	Version
28	Period
29-31	Extension, LBL or TAB

The tabular files are formatted so that they may be read directly into many database management systems (DBMS) or spreadsheet programs on various computers. Each of the files contains two tables. The first is the header table, and is only a single record in length. The second table contains all of the data records for a session and varies in length.

All fields in the tables are stored in columns of fixed width and are right justified. The records are of fixed length; since the header records are shorter than the data records, they have been padded with blank spaces at the end of the record. The last two bytes of each record contain the ASCII carriage return and line feed characters. This allows the tables to be treated as fixed length record files on computers that support this file type and as normal text files on other computers.

The PDS labels are object-oriented. The object to which the labels refer (the tables) is denoted by a statement of the form:

^object = location

in which the carat character ('^', also called a pointer in this context) indicates that the object starts at the given location. For an object located outside the label file (as in this case), the location denotes the name of the file containing the object, along with the starting record. For example:

^TABLE = 'MS013RLP_00126907202_15C6M1.TAB'

indicates that the TABLE object is in the same directory as the detached label file. (Records are counted starting at 1, not 0.)

The detached label files are stream format files, with a carriage return (ASCII 13) and a line feed character (ASCII 10) at the end of each record. This allows the files to be read by the MacOS, DOS, UNIX, and VMS operating systems.

Software

The EDR/RDR tables can be displayed on UNIX, Macintosh, and PC platforms as simple ASCII files, or using the PDS developed program, NASAView. This software is freely available from the PDS Central Node and may be obtained from their web site at http://pds.jpl.nasa.gov/.

Data Set Overview

The Phoenix Mars Lander arrived at 68.2184N, 234.2487E on May 25, 2008.

The PHX Atmospheric Lidar Profiles product contains raw laser scattering atmospheric profiles (i.e profiles in counts or volts, but not corrected for all instrumental effects). Each operation of the lidar instrument is provided as a separate product, and often more than one operation was conducted per sol.

The RDR Data are organized into Photon Counting (532nm), Analog (532 & 1064nm) and Supplemental (Laser Power, Lidar Background Skylight and sensorhead temperatures).

The lidar instrument is highly configurable, leading to a myriad of possible data volume outcomes. Briefly, a single (vertical) profile of atmospheric scattering is given for a single point in time, and listed as values at various ranges (distance) from the lander (with the difference between successive ranges defining the sampling range interval). Successive profiles, marked with a separate time, determine the temporal sampling interval (period duration), and the total duration is defined as the product of total number of profiles and sampling interval (temporal integration duration). The range sampling interval for analog and photon counting channels can be configured separately,

Supplemental data contains the average, min and max laser voltages (provided as an estimate of laser power); inter_pulse analog background values; and sensor-head temperature estimates, as an indicator of co-alignment between laser transmitter and receiver. [WHITEWAY2008]

The Data is organized by a unique identifier (Token) is keeping with the other Phoenix instruments. The token for the Lidar was set each instance of operation, and is provided as a 4 byte hex value.

Every record is stored with both the spacecraft time, and UTC start time, and each data record can thus be retrieved from each table using time as a common key.

Parameters

Each RDR file contains time as fractions of a seconds since START_TIME. The range that scattering occurs at is given from the lander deck (approximately vertical) in meters.

The number of profiles and integration duration are also provided for reference.

During surface operations, the range resolution was nominally set to 20m and 50m, respectively, for the analog and photon counting data; The sampling period was between 1.28 - 20.48 sec, with the vast majority of lidar operations employing 20.24 sec resolution; each operation of the lidar was between 5 and 90 min in total duration, with the average operation lasting 20 min.

Processing

The RDR products have had the following changes as compared to the EDRs:

1. The data has been changed and reordered where required to be consistent with the SIS.

2. The Frame Count is converted to the duration of each measurement in Earth seconds.

3. Digital Numbers have been converted to Volts given:

Volts = (DN / NLSIP / RSD) * -8.929312609 + 0.7314 (NLSIP = Number of Laser Shots per Integration Period NSD = Range Sampling Distance (e.g. 50m) / 2.5)

Finally, the data were converted to PDS format, converting the tab-delimited fields to fixed-width fields, and exchanging the multiple packet headers for a single session header by the MET GDS.

Data

All of the data in this data set are contained in ASCII tabular files with detached PDS labels. Data is stored in a separate directory relating to the sol in which the recording of data commenced (i.e. data acquired from 003 10:00 local to 004 10:15 will be in the sol 3 directory)

Individual filenames are constructed as follows:

MS002RLP_00896227243_10CCM0.LBL
1	The first character will always be an 'M', representing MET data.
2	The second character will be an 'S', signifying surface data (versus 'C' for Cruise)
3-5	The next three characters provide the sol number of the data file.
6-8	The next three characters describe the type of MET data, ELP - EDR Lidar Photon Counting *532 nm) ELA - EDR Lidar Analog (532 & 1064 nm) ELS - EDR Lidar Supplemental Data RLP - RDR Lidar Photon Counting *532 nm) RLA - RDR Lidar Analog (532 & 1064 nm) RLS - RDR Lidar Supplemental Data
9	Blank
10-20	SCLK - Spacecraft clock
21	Blank
22-25	Operations Token
26	Producer (M for MET Team)
27	Version
28	Period
29-31	Extension, LBL or TAB

The tabular files are formatted so that they may be read directly into many database management systems (DBMS) or spreadsheet programs on various computers. Each of the files contains two tables. The first is the header table, and is only a single record in length. The second table contains all of the data records for a session and varies in length.

All fields in the tables are stored in columns of fixed width and are right justified. The records are of fixed length; since the header records are shorter than the data records, they have been padded with blank spaces at the end of the record. The last two bytes of each record contain the ASCII carriage return and line feed characters. This allows the tables to be treated as fixed length record files on computers that support this file type and as normal text files on other computers.

The PDS labels are object-oriented. The object to which the labels refer (the tables) is denoted by a statement of the form:

^object = location

in which the carat character ('^', also called a pointer in this context) indicates that the object starts at the given location. For an object located outside the label file (as in this case), the location denotes the name of the file containing the object, along with the starting record. For example:

^TABLE = 'MS013RLP_00126907202_15C6M1.TAB'

indicates that the TABLE object is in the same directory as the detached label file. (Records are counted starting at 1, not 0.)

The detached label files are stream format files, with a carriage return (ASCII 13) and a line feed character (ASCII 10) at the end of each record. This allows the files to be read by the MacOS, DOS, UNIX, and VMS operating systems.

Software

The EDR/RDR tables can be displayed on UNIX, Macintosh, and PC platforms as simple ASCII files, or using the PDS developed program, NASAView. This software is freely available from the PDS Central Node and may be obtained from their web site at http://pds.jpl.nasa.gov/.