| DATA_SET_DESCRIPTION |
Modification History
====================
Version 1 data volumes include volumes LS003 through LS029, released
Dec 2008. These volumes contain Lidar data collected May 2008
through June 2008, specifically Sols 3-29.
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.
Address: Cameron Dickinson
Dept. of Earth and Space Science Engineering
York University
4700 Keele St
Toronto, ON M3J 1P3
Phone: (416) 736-2100 X 23870
Email: cameron.dickinson@gmail.com
For science related questions about the data, please contact the
MET Instrument Science Team Lead:
Address: James Whiteway
Dept. of Earth and Space Science Engineering
York University
4700 Keele St
Toronto, ON M3J 1P3
Phone: (416) 736-2100 X 22310
Email: whiteway@yorku.ca
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.nasa.gov/. For more information or help in obtaining
the software, contact the PDS operator at the following address:
Address: Planetary Data System, PDS Operator
Jet Propulsion Laboratory
4800 Oak Grove Drive
Pasadena, CA 91109
Phone: (818) 354-4321
Email: pds_operator@jpl.nasa.gov
WWW URL: http://pds.nasa.gov/
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