> **LANDSAT DATA CONTINUITY MISSION**
>
> **ACRONYM LIST AND LEXICON**
>
> **November 2, 2006**
>
> ![](media/image1.png)

# ![](media/image2.pct){width="1.0416666666666666e-2in" height="1.0416666666666666e-2in"}LDCM PROJECT DOCUMENT CHANGE RECORD  {#ldcm-project-document-change-record .unnumbered}

Sheet: 1 of 1

+--------------+-------------------------------------+-----------------+
| REV          | DESCRIPTION OF CHANGE               | DATE            |
|              |                                     |                 |
| LEVEL        |                                     | APPROVED        |
+--------------+-------------------------------------+-----------------+
|              |                                     |                 |
+--------------+-------------------------------------+-----------------+

#  List of TBDs/TBRs {#list-of-tbdstbrs .unnumbered}

+----+------------+----------------------------------+-------+-------+
| ## | ######     | ############                     | ##    | #     |
| ## | ####### Lo | # Summary {#summary .unnumbered} | ##### | ##### |
| ## | cation {#l |                                  | ##### | ##### |
| ## | ocation .u |                                  | # Ind | ## Du |
| ## | nnumbered} |                                  | ./Org | e Dat |
| ## |            |                                  | . {#i | e {#d |
| #  |            |                                  | nd.or | ue-da |
| It |            |                                  | g. .u | te .u |
| em |            |                                  | nnumb | nnumb |
|  N |            |                                  | ered} | ered} |
| o. |            |                                  |       |       |
|  { |            |                                  |       |       |
| #i |            |                                  |       |       |
| te |            |                                  |       |       |
| m- |            |                                  |       |       |
| no |            |                                  |       |       |
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| um |            |                                  |       |       |
| be |            |                                  |       |       |
| re |            |                                  |       |       |
| d} |            |                                  |       |       |
+====+============+==================================+=======+=======+
| #  | #########  | ############# Data c             | ####  | ####  |
| ## | ####  {#se | urrently not compiled {#data-cur | ##### | ##### |
| ## | ction-1 .u | rently-not-compiled .unnumbered} | ####  | ####  |
| ## | nnumbered} |                                  |  {#se |  {#se |
| ## |            |                                  | ction | ction |
| ## |            |                                  | -2 .u | -3 .u |
| ## |            |                                  | nnumb | nnumb |
|    |            |                                  | ered} | ered} |
| {# |            |                                  |       |       |
| se |            |                                  |       |       |
| ct |            |                                  |       |       |
| io |            |                                  |       |       |
| n  |            |                                  |       |       |
| .u |            |                                  |       |       |
| nn |            |                                  |       |       |
| um |            |                                  |       |       |
| be |            |                                  |       |       |
| re |            |                                  |       |       |
| d} |            |                                  |       |       |
+----+------------+----------------------------------+-------+-------+
| #  | #########  | #######                          | ####  | ####  |
| ## | ####  {#se | ######  {#section-6 .unnumbered} | ##### | ##### |
| ## | ction-5 .u |                                  | ####  | ####  |
| ## | nnumbered} |                                  |  {#se |  {#se |
| ## |            |                                  | ction | ction |
| ## |            |                                  | -7 .u | -8 .u |
| ## |            |                                  | nnumb | nnumb |
|    |            |                                  | ered} | ered} |
| {# |            |                                  |       |       |
| se |            |                                  |       |       |
| ct |            |                                  |       |       |
| io |            |                                  |       |       |
| n- |            |                                  |       |       |
| 4  |            |                                  |       |       |
| .u |            |                                  |       |       |
| nn |            |                                  |       |       |
| um |            |                                  |       |       |
| be |            |                                  |       |       |
| re |            |                                  |       |       |
| d} |            |                                  |       |       |
+----+------------+----------------------------------+-------+-------+
| #  | ########## | ########                         | ##### | ##### |
| ## | ###  {#sec | #####  {#section-11 .unnumbered} | ##### | ##### |
| ## | tion-10 .u |                                  | ###   | ###   |
| ## | nnumbered} |                                  | {#sec | {#sec |
| ## |            |                                  | tion- | tion- |
| ## |            |                                  | 12 .u | 13 .u |
| ## |            |                                  | nnumb | nnumb |
|    |            |                                  | ered} | ered} |
| {# |            |                                  |       |       |
| se |            |                                  |       |       |
| ct |            |                                  |       |       |
| io |            |                                  |       |       |
| n- |            |                                  |       |       |
| 9  |            |                                  |       |       |
| .u |            |                                  |       |       |
| nn |            |                                  |       |       |
| um |            |                                  |       |       |
| be |            |                                  |       |       |
| re |            |                                  |       |       |
| d} |            |                                  |       |       |
+----+------------+----------------------------------+-------+-------+

# TABLE OF CONTENTS {#table-of-contents .unnumbered}

Page

[LDCM PROJECT DOCUMENT CHANGE RECORD
ii](#ldcm-project-document-change-record)

[List of TBDs/TBRs iii](#list-of-tbdstbrs)

[TABLE OF CONTENTS iv](#table-of-contents)

[1.0 ACRONYM LIST 5](#acronym-list)

[2.0 LEXICON 14](#lexicon)

# ACRONYM LIST

+------------+---------------------------------------------------------+
| **ABML**   | As-Built Materials List                                 |
+------------+---------------------------------------------------------+
| **ABPL**   | As-Built Parts List                                     |
+------------+---------------------------------------------------------+
| **ADF**    | Ancillary Data File                                     |
+------------+---------------------------------------------------------+
| **ADML**   | As-Designed Materials List                              |
+------------+---------------------------------------------------------+
| **ADPL**   | As-Designed Parts List                                  |
+------------+---------------------------------------------------------+
| **AFB**    | United States Air Force Base                            |
+------------+---------------------------------------------------------+
| **ALI**    | Advanced Land Imager                                    |
+------------+---------------------------------------------------------+
| #### ANSI  | American National Standards Institute                   |
|  {#ansi .u |                                                         |
| nnumbered} |                                                         |
+------------+---------------------------------------------------------+
| #### AO    | Acquisition of Signal                                   |
| S {#aos .u |                                                         |
| nnumbered} |                                                         |
+------------+---------------------------------------------------------+
| #### ASIC  | Application Specific Integrated Circuits                |
|  {#asic .u |                                                         |
| nnumbered} |                                                         |
+------------+---------------------------------------------------------+
| #### ASQC  | American Society for Quality Control                    |
|  {#asqc .u |                                                         |
| nnumbered} |                                                         |
+------------+---------------------------------------------------------+
| #### ASTM  | American Society for Testing of Materials               |
|  {#astm .u |                                                         |
| nnumbered} |                                                         |
+------------+---------------------------------------------------------+
| #### BE    | Bit Error Rate                                          |
| R {#ber .u |                                                         |
| nnumbered} |                                                         |
+------------+---------------------------------------------------------+
| #### BRDF  | Bi-directional Reflectance Distribution Function        |
|  {#brdf .u |                                                         |
| nnumbered} |                                                         |
+------------+---------------------------------------------------------+
| **C&DH**   | Command and Data Handling                               |
+------------+---------------------------------------------------------+
| **CADU**   | Channel Access Data Unit                                |
+------------+---------------------------------------------------------+
| **CAGE**   | Commercial and Government Entity                        |
+------------+---------------------------------------------------------+
| **CCP**    | Contamination Control Plan                              |
+------------+---------------------------------------------------------+
| **CCSDS**  | Consultative Committee on Space Data Systems            |
+------------+---------------------------------------------------------+
| **CDR**    | Critical Design Review                                  |
+------------+---------------------------------------------------------+
| **CDRL**   | Contract Data Requirements List                         |
+------------+---------------------------------------------------------+
| **CFR**    | Code of Federal Regulations                             |
+------------+---------------------------------------------------------+
| **CIL**    | Critical Items List                                     |
+------------+---------------------------------------------------------+
| **CM**     | Configuration Management                                |
+------------+---------------------------------------------------------+
| **CN**     | Coherent Noise                                          |
+------------+---------------------------------------------------------+
| **CNDs**   | Could-Not-Duplicates                                    |
+------------+---------------------------------------------------------+
| **CO**     | Contracting Officer                                     |
+------------+---------------------------------------------------------+
| **COC**    | Certificate of Completion                               |
+------------+---------------------------------------------------------+
| **COG**    | Center of Gravity                                       |
+------------+---------------------------------------------------------+
| **COTR**   | Contracting Officer's Technical Representative          |
+------------+---------------------------------------------------------+
| **COTS**   | Commercial Off-The-Shelf                                |
+------------+---------------------------------------------------------+
| **CPT**    | Comprehensive Performance Test                          |
+------------+---------------------------------------------------------+
| **CPU**    | Central Processing Unit                                 |
+------------+---------------------------------------------------------+
| **CRM**    | Continuous Risk Management                              |
+------------+---------------------------------------------------------+
| **CTE**    | Calibration Test Equipment                              |
+------------+---------------------------------------------------------+
| **CVCM**   | Collected Volatile Condensable Mass                     |
+------------+---------------------------------------------------------+
| **DACA**   | Days After Contract Award                               |
+------------+---------------------------------------------------------+
| **DC**     | Direct Current                                          |
+------------+---------------------------------------------------------+
| **DCN**    | Documentation Change Notices                            |
+------------+---------------------------------------------------------+
| **DDD**    | Displacement Damage Dose                                |
+------------+---------------------------------------------------------+
| **DID**    | Data Item Description                                   |
+------------+---------------------------------------------------------+
| **DM**     | Data Management                                         |
+------------+---------------------------------------------------------+
| **DN**     | Digital Number                                          |
+------------+---------------------------------------------------------+
| **DoD**    | Department of Defense                                   |
+------------+---------------------------------------------------------+
| **DOI**    | Department of the Interior                              |
+------------+---------------------------------------------------------+
| **DPA**    | Destructive Physical Analysis                           |
+------------+---------------------------------------------------------+
| **DRFP**   | Draft Request for Proposal                              |
+------------+---------------------------------------------------------+
| **DUNS**   | Data Universal Numbering System                         |
+------------+---------------------------------------------------------+
| **EC**     | Electronic Copy                                         |
+------------+---------------------------------------------------------+
| **ECI**    | Earth Centered Inertial                                 |
+------------+---------------------------------------------------------+
| **EDAC**   | Error Detection and Correction                          |
+------------+---------------------------------------------------------+
| **EDU**    | Engineering Development Unit                            |
+------------+---------------------------------------------------------+
| **EEE**    | Electrical, Electronic, Electromechanical               |
+------------+---------------------------------------------------------+
| **EIA**    | Electronic Industry Alliance                            |
+------------+---------------------------------------------------------+
| **ELV**    | Expendable Launch Vehicle                               |
+------------+---------------------------------------------------------+
| **EMC**    | Electromagnetic Compatibility                           |
+------------+---------------------------------------------------------+
| **EMI**    | Electromagnetic Interference                            |
+------------+---------------------------------------------------------+
| **EO-1**   | Earth Observer 1                                        |
+------------+---------------------------------------------------------+
| **EOL**    | End of Life                                             |
+------------+---------------------------------------------------------+
| **EOS**    | Earth Observing System                                  |
+------------+---------------------------------------------------------+
| **EROS**   | Earth Resources Observation and Science                 |
+------------+---------------------------------------------------------+
| **ESD**    | Electrostatic Discharge                                 |
+------------+---------------------------------------------------------+
| **ETM+**   | Enhanced Thematic Mapper Plus                           |
+------------+---------------------------------------------------------+
| **EVP**    | Environmental Verification Plan                         |
+------------+---------------------------------------------------------+
| **EVS**    | Earned Value System                                     |
+------------+---------------------------------------------------------+
| **EWR**    | Eastern and Western Ranges                              |
+------------+---------------------------------------------------------+
| **FAR**    | Federal Acquisition Regulation                          |
+------------+---------------------------------------------------------+
| **FDC**    | Failure Detection and Correction                        |
+------------+---------------------------------------------------------+
| **FGDC**   | Federal Geographic Data Committee                       |
+------------+---------------------------------------------------------+
| **FMECA**  | Failure Modes, Effects and Criticality Analysis         |
+------------+---------------------------------------------------------+
| **FOR**    | Flight Operations Review                                |
+------------+---------------------------------------------------------+
| **FOV**    | Field of View                                           |
+------------+---------------------------------------------------------+
| **FPA**    | Focal Plane Array                                       |
+------------+---------------------------------------------------------+
| **FPE**    | Focal Plane Electronics                                 |
+------------+---------------------------------------------------------+
| **FRB**    | Failure Review Board                                    |
+------------+---------------------------------------------------------+
| **FTA**    | Fault Tree Analysis                                     |
+------------+---------------------------------------------------------+
| **FWHM**   | Full Width Half Maximum                                 |
+------------+---------------------------------------------------------+
| **GAO**    | General Accounting Office                               |
+------------+---------------------------------------------------------+
| **GDS**    | Ground Data Systems                                     |
+------------+---------------------------------------------------------+
| **GEVS**   | General Environmental Verification Specification        |
+------------+---------------------------------------------------------+
| **GFE**    | Government Furnished Equipment                          |
+------------+---------------------------------------------------------+
| **GFY**    | Government Fiscal Year                                  |
+------------+---------------------------------------------------------+
| **GIA**    | Government Inspection Agency                            |
+------------+---------------------------------------------------------+
| **GIDEP**  | Government Industry Data Exchange Program               |
+------------+---------------------------------------------------------+
| **GOP**    | Ground Operations Plan                                  |
+------------+---------------------------------------------------------+
| **GPD**    | GSFC Policy Directive                                   |
+------------+---------------------------------------------------------+
| **GPS**    | Global Positioning System                               |
+------------+---------------------------------------------------------+
| **GSD**    | Ground Sample(ing) Distance                             |
+------------+---------------------------------------------------------+
| **GSE**    | Ground Support Equipment                                |
+------------+---------------------------------------------------------+
| **GSFC**   | Goddard Space Flight Center                             |
+------------+---------------------------------------------------------+
| **HC**     | Hard Copy                                               |
+------------+---------------------------------------------------------+
| **HUB**    | Historically Underutilized Business                     |
+------------+---------------------------------------------------------+
| **I&T**    | Integration and Test                                    |
+------------+---------------------------------------------------------+
| **IAC**    | Independent Assurance Contractor                        |
+------------+---------------------------------------------------------+
| **IC**     | International Cooperator                                |
+------------+---------------------------------------------------------+
| **ICD**    | Interface Control Document                              |
+------------+---------------------------------------------------------+
| **IDF**    | Image Data File                                         |
+------------+---------------------------------------------------------+
| **IOC**    | Initial Operational Capability                          |
+------------+---------------------------------------------------------+
| **IPC**    | Institute for Interconnecting and Packaging Electronic  |
|            | Circuits                                                |
+------------+---------------------------------------------------------+
| **IPSR**   | Instrument Pre-Ship Review                              |
+------------+---------------------------------------------------------+
| **IRD**    | Interface Requirements Document                         |
+------------+---------------------------------------------------------+
| **IRU**    | Inertial Reference Unit                                 |
+------------+---------------------------------------------------------+
| **ISO**    | International Organization for Standardization          |
+------------+---------------------------------------------------------+
| **ITAR**   | International Traffic in Arms Regulations               |
+------------+---------------------------------------------------------+
| **IV&V**   | Independent Verification and Validation                 |
+------------+---------------------------------------------------------+
| **KHB**    | Kennedy Space Center Handbook                           |
+------------+---------------------------------------------------------+
| **LDCM**   | Landsat Data Continuity Mission                         |
+------------+---------------------------------------------------------+
| **LGS**    | Landsat Ground Station                                  |
+------------+---------------------------------------------------------+
| **LGN**    | LDCM Ground Network                                     |
+------------+---------------------------------------------------------+
| **Lmax**   | Maximum Radiance                                        |
+------------+---------------------------------------------------------+
| **LMST**   | Local Mean Solar Time                                   |
+------------+---------------------------------------------------------+
| **LOS**    | Line of Sight or                                        |
|            |                                                         |
|            | Loss of Signal                                          |
+------------+---------------------------------------------------------+
| **LPT**    | Limited Performance Test                                |
+------------+---------------------------------------------------------+
| **LRR**    | Launch Readiness Review                                 |
+------------+---------------------------------------------------------+
| **LTAP**   | Long Term Acquisition Plan                              |
+------------+---------------------------------------------------------+
| **         | Typical Radiance                                        |
| Ltypical** |                                                         |
+------------+---------------------------------------------------------+
| **M&PCB**  | Materials and Processes Control Board                   |
+------------+---------------------------------------------------------+
| **M&PCP**  | Materials and Processes Control Program                 |
+------------+---------------------------------------------------------+
| **MAE**    | Materials Assurance Engineer                            |
+------------+---------------------------------------------------------+
| **MAM**    | Mission Assurance Manager                               |
+------------+---------------------------------------------------------+
| **MAR**    | Mission Assurance Requirements                          |
+------------+---------------------------------------------------------+
| **MCM**    | Multi-Chip Module                                       |
+------------+---------------------------------------------------------+
| **MEB**    | Materials Engineering Branch                            |
+------------+---------------------------------------------------------+
| **MIL**    | Materials Identification List                           |
+------------+---------------------------------------------------------+
| **MOC**    | Mission Operations Control Center                       |
+------------+---------------------------------------------------------+
| **MODIS**  | Moderate Resolution Imaging Spectrometer                |
+------------+---------------------------------------------------------+
| *          | Moderate Resolution Transmittance                       |
| *MODTRAN** |                                                         |
+------------+---------------------------------------------------------+
| **MOI**    | Moment of Inertia                                       |
+------------+---------------------------------------------------------+
| **MOR**    | Mission Operations Review                               |
+------------+---------------------------------------------------------+
| **MPR**    | Monthly Progress Review                                 |
+------------+---------------------------------------------------------+
| **MPSR**   | Management Program Status Review                        |
+------------+---------------------------------------------------------+
| **MRB**    | Material Review Board                                   |
+------------+---------------------------------------------------------+
| **MSFC**   | Marshall Space Flight Center                            |
+------------+---------------------------------------------------------+
| **MSPSP**  | Missile System Prelaunch Safety Data Package            |
+------------+---------------------------------------------------------+
| **MUA**    | Materials Usage Agreement                               |
+------------+---------------------------------------------------------+
| **NAS**    | NASA Assurance Standard                                 |
+------------+---------------------------------------------------------+
| **NASA**   | National Aeronautics and Space Administration           |
+------------+---------------------------------------------------------+
| **NASCOM** | NASA Communications Network                             |
+------------+---------------------------------------------------------+
| **NDE**    | Non-Destructive Examination                             |
+------------+---------------------------------------------------------+
| **NDVI**   | Normalized Difference Vegetation Index                  |
+------------+---------------------------------------------------------+
| **NEPAG**  | NASA EEE Parts Assurance Group                          |
+------------+---------------------------------------------------------+
| **NHB**    | NASA Handbook                                           |
+------------+---------------------------------------------------------+
| **NIR**    | Near Infrared                                           |
+------------+---------------------------------------------------------+
| **NIST**   | National Institute of Standards and Technology          |
+------------+---------------------------------------------------------+
| **NPD**    | NASA Policy Directive                                   |
+------------+---------------------------------------------------------+
| **NPSL**   | NASA Parts Selection List                               |
+------------+---------------------------------------------------------+
| **NRCA**   | Nonconformance Reporting and Corrective Action          |
+------------+---------------------------------------------------------+
| **NSPAR**  | Nonstandard Parts Approval Request                      |
+------------+---------------------------------------------------------+
| **NSS**    | NASA Safety Standard                                    |
+------------+---------------------------------------------------------+
| **NTE**    | Not To Exceed                                           |
+------------+---------------------------------------------------------+
| **NUC**    | Non-Uniformity Correction                               |
+------------+---------------------------------------------------------+
| **OBP**    | On-Board Processor                                      |
+------------+---------------------------------------------------------+
| **OLI**    | Operational Land Imager                                 |
+------------+---------------------------------------------------------+
| **OMB**    | Office of Management and Budget                         |
+------------+---------------------------------------------------------+
| **OSHA**   | Occupational Safety and Health Administration           |
+------------+---------------------------------------------------------+
| **OSSMA**  | GSFC Office of Systems Safety and Mission Assurance     |
+------------+---------------------------------------------------------+
| **PAPL**   | Project Approved Parts List                             |
+------------+---------------------------------------------------------+
| **PCB**    | Parts Control Board                                     |
+------------+---------------------------------------------------------+
| **PCP**    | Parts Control Plan                                      |
+------------+---------------------------------------------------------+
| **PDL**    | Product Design Lead                                     |
+------------+---------------------------------------------------------+
| **PDR**    | Preliminary Design Review                               |
+------------+---------------------------------------------------------+
| **PER**    | Performance Evaluation Review or                        |
|            |                                                         |
|            | Pre-Environmental review                                |
+------------+---------------------------------------------------------+
| **PF**     | Polarization Factor                                     |
+------------+---------------------------------------------------------+
| **PFR**    | Problem / Failure Report                                |
+------------+---------------------------------------------------------+
| **PIL**    | Parts Identification List                               |
+------------+---------------------------------------------------------+
| **PM**     | Program Management                                      |
+------------+---------------------------------------------------------+
| **PPL**    | Preferred Parts List                                    |
+------------+---------------------------------------------------------+
| **PR**     | Program Review                                          |
+------------+---------------------------------------------------------+
| **PRA**    | Probabilistic Risk Assessment                           |
+------------+---------------------------------------------------------+
| **PSD**    | Power Spectral Density                                  |
+------------+---------------------------------------------------------+
| **PSM**    | Project Safety Manager                                  |
+------------+---------------------------------------------------------+
| **PSR**    | Program Status Review or                                |
|            |                                                         |
|            | Pre-Shipment Review                                     |
+------------+---------------------------------------------------------+
| **PWB**    | Printed Wiring Board                                    |
+------------+---------------------------------------------------------+
| **QA**     | Quality Assurance                                       |
+------------+---------------------------------------------------------+
| **QCM**    | Quartz Crystal Microbalance                             |
+------------+---------------------------------------------------------+
| **QMS**    | Quality Management System                               |
+------------+---------------------------------------------------------+
| **RBS**    | Reflective Band Sensor                                  |
+------------+---------------------------------------------------------+
| **RF**     | Radio Frequency                                         |
+------------+---------------------------------------------------------+
| **RFP**    | Request for Proposal                                    |
+------------+---------------------------------------------------------+
| **ROI**    | Return on Investment                                    |
+------------+---------------------------------------------------------+
| **SC**     | Spacecraft                                              |
+------------+---------------------------------------------------------+
| **SCC**    | Stress Corrosion Cracking                               |
+------------+---------------------------------------------------------+
| **SCM**    | Software Configuration Management                       |
+------------+---------------------------------------------------------+
| **SCR**    | System Concept Review                                   |
+------------+---------------------------------------------------------+
| **SDR**    | System Design Review                                    |
+------------+---------------------------------------------------------+
| **SDMP**   | Software Development and Management Plan                |
+------------+---------------------------------------------------------+
| **SE**     | Systems Engineering                                     |
+------------+---------------------------------------------------------+
| **SEE**    | Single-Event Effect                                     |
+------------+---------------------------------------------------------+
| **SEL**    | Single-Event Latchup                                    |
+------------+---------------------------------------------------------+
| **SEU**    | Single-Event Upset                                      |
+------------+---------------------------------------------------------+
| **SI**     | Science Instrument                                      |
+------------+---------------------------------------------------------+
| **SMA**    | Safety and Mission Assurance                            |
+------------+---------------------------------------------------------+
| **SMD**    | Stored Mission Data                                     |
+------------+---------------------------------------------------------+
| **SNR**    | Signal to Noise Ratio                                   |
+------------+---------------------------------------------------------+
| **SOW**    | Statement of Work                                       |
+------------+---------------------------------------------------------+
| **SPSR**   | System Pre-Ship Review                                  |
+------------+---------------------------------------------------------+
| **SPVP**   | System Performance Verification Plan                    |
+------------+---------------------------------------------------------+
| **SQA**    | Software Quality Assurance                              |
+------------+---------------------------------------------------------+
| **SQMS**   | Software Quality Management System                      |
+------------+---------------------------------------------------------+
| **SR**     | System Review                                           |
+------------+---------------------------------------------------------+
| **SRO**    | Systems Review Office                                   |
+------------+---------------------------------------------------------+
| **SDR**    | System Design Review                                    |
+------------+---------------------------------------------------------+
| **SRR**    | System Requirements Review                              |
+------------+---------------------------------------------------------+
| **SRT**    | Systems Review Team                                     |
+------------+---------------------------------------------------------+
| **SSIP**   | System Safety Implementation Plan                       |
+------------+---------------------------------------------------------+
| **STE**    | System Test Equipment                                   |
+------------+---------------------------------------------------------+
| **STM**    | Structural Thermal Model                                |
+------------+---------------------------------------------------------+
| **SW**     | Software                                                |
+------------+---------------------------------------------------------+
| **SWIR**   | Short Wave Infrared                                     |
+------------+---------------------------------------------------------+
| **T/V**    | Thermal/Vacuum                                          |
+------------+---------------------------------------------------------+
| **TBC**    | To Be Confirmed                                         |
+------------+---------------------------------------------------------+
| **TBD**    | To Be Determined                                        |
+------------+---------------------------------------------------------+
| **TBR**    | To Be Reviewed or                                       |
|            |                                                         |
|            | To Be Resolved                                          |
+------------+---------------------------------------------------------+
| **TBS**    | To Be Supplied                                          |
+------------+---------------------------------------------------------+
| **TDI**    | Time Delay Integration                                  |
+------------+---------------------------------------------------------+
| **TID**    | Total Ionizing Dose                                     |
+------------+---------------------------------------------------------+
| **TIM**    | Technical Interchange Meeting                           |
+------------+---------------------------------------------------------+
| **TIRS**   | Thermal Infrared Sensor                                 |
+------------+---------------------------------------------------------+
| **TML**    | Total Mass Loss                                         |
+------------+---------------------------------------------------------+
| **TQCM**   | Thermoelectric Quartz Crystal Microbalance              |
+------------+---------------------------------------------------------+
| **USG**    | United States Government                                |
+------------+---------------------------------------------------------+
| **USGS**   | United States Geological Survey                         |
+------------+---------------------------------------------------------+
| **V&V**    | Verification and Validation                             |
+------------+---------------------------------------------------------+
| **VNIR**   | Visible and Near Infrared                               |
+------------+---------------------------------------------------------+
| **VTL**    | Verification Tracking Log                               |
+------------+---------------------------------------------------------+
| **WBS**    | Work Breakdown Structure                                |
+------------+---------------------------------------------------------+
| **WGS84**  | World Geodetic System 1984                              |
+------------+---------------------------------------------------------+

# LEXICON

**Allocation --** An allocation is a requirement which is derived by
partitioning a higher level requirement into lower level component
requirements and making an assignment of values to that lower level.
Allocation statements use the verb "shall".

**Ancillary Data** - A selected subset of observatory telemetry that
provides information about the on-orbit environment and observatory
status at the time of the image sensor data collections. Ancillary data
shall include all observatory telemetry necessary to produce a scene
data product. Ancillary data typically includes relevant instrument
parameters, calibration parameters, observatory attitude and ephemeris,
etc.

**Attitude reference frame knowledge -** The pointing information for
the three orthogonal axes of rotation as calculated by the observatory
attitude control system and displayed in observatory housekeeping
telemetry. It is expressed as an angular rotation offset about each axis
from a pre-defined nominal pointing orientation.

**Authentication --** Security measure designed to establish the
validity of a transmission, message, or originator. Authentication
provides the assurance that information transmitted from a claimed
source (i.e., a source\'s identity) actually came from that source.

**Auxiliary Data --** Supporting data sets provided outside the Space
Segment data stream used to apply corrections to the Space Segment
sensor data. Examples include: previously derived calibration
parameters, ground control data, digital elevation data, and GPS offset
data.

**Audit --** A review of the developers, contractor\'s or
subcontractor\'s documentation or hardware to verify that it complies
with project requirements.

**Azimuth --** Angle measured in the ecliptic or equatorial plane as
part of a spherical polar coordinate system (radius or altitude, azimuth
and elevation).

**Bi-directional Reflectance Distribution Function (BRDF)** - A function
that expresses reflectance from a surface into a unit projected solid
angle as a function of both the direction of illumination and the
direction of observation.

**Bright Target Recovery** - The recovery of the system from a
saturation event such as a sun glint

**Calibrate** - The process of characterizing system behavior to a known
standard or controlled input. Calibration is performed to determine
correction parameters (e.g. gains and offsets) that can be applied to
the data to correct for systematic errors.

**Calibration Maneuver --** A spacecraft attitude adjustment made to
view a calibration source (i.e. deep space, moon, earth limb, ground
target).

**Channel Access Data Unit (CADU) --** A Channel Access Data Unit is a
CCSDS-defined frame format.

**Characterize** -- The use of a set of measurements and analyses to
describe the performance of a device or product over the relevant
operating range. This includes taking point measurements, modeling the
variation in a characteristic as a function of one or more parameters
(e.g., temperature, time), measuring stability over a range of
conditions, and computing error estimates.

**Coherent Noise** - A spurious, periodic pattern of noise within an
image, generally of electronic origin.

**Collect --** to acquire, downlink, and subsequently transfer of
mission data from the observatory to the Data Processing and Archive
Segment

**Collected Volatile Condensable Material (CVCM)** - The quantity of out
gassed matter from a test specimen that condenses on a collector
maintained at a specific constant temperature for a specified time.

**Contact:** A single satellite AOS to LOS session taken at either a
ground station or a communication satellite such as TDRSS.

**Dark Detectors** - Detectors on the focal plane of the instrument that
are masked from receiving all incoming light, but are otherwise
identical to the detectors observing the Earth reflected radiation.

**Dead Pixels** -- See Inoperable Pixels

**Definitive Ephemeris** **Data** - A data set that provides a post
processed, time varying, orbital states derived from a set of
observations. Typically, this includes the position, velocity and time
expressed over a regular time interval.

**Demonstrate** - Show that the current knowledge of one or more system
parameters is correct and accurate by collecting and processing test
data using current calibration parameters, and analyzing the performance
of the processed results.

**Detector --** A single physical sensing element that produces an
electrical output in response to incident electromagnetic radiation. If
time delayed integration (TDI) is used, the outputs of multiple
detectors in a column are summed to produce a single output. This single
output may also be considered as the output of a single "detector".

**Detector Column** - A set of physical detectors imaging the same
spatial locations for a single band, which are treated as a single
sensing element by having their outputs combined in time-delay
integration (TDI).

**Digital Number** **(DN)** - The output from a detector sample
quantized to a discrete integer value.

**Discrepancy -** Refer to Nonconformance

**Displacement Damage -** Degradation in a bipolar or opto-electronic
device resulting from displacement of atoms in the semiconductor lattice
by energetic particles.

**Dynamic Range** - The range of radiances over which instruments and
sensors are sensitive. The upper end of the dynamic range is the
saturation radiance. The lower end is the noise floor, i.e., the
radiance corresponding to the low radiance noise level of the
instrument. These radiances may be expressed as equivalent blackbody
temperatures for thermal bands.

**Edge Response** - The response of an imaging system to an edge target
(i.e., a low/high or high/low step function), normalized so that the
mean response on the low side of the edge target is set to zero and the
mean response on the high side of the edge target is set to 100%.

**Encryption:** Security measure designed to prevent unauthorized access
to data or control of the observatory. Encryption is achieved by
converting plain text to equivalent cipher text by means of a code.

**Ephemeris** **Data** - A set of data that provides the position,
velocity and time of a celestial body (including a manmade satellite)
for regular intervals. Ephemeris data helps to characterize the
conditions under which remote sensing data are collected and may be used
to correct the sensor data prior to analysis.

**Expedited Production --** Expedited production is defined as orders
for LDCM data products to be generated from the archive with a rapid
(expedited) turnaround time.

**Failure Modes, Effects and Criticality Analysis (FMECA) -** A
procedure by which each credible failure mode of each item from a low
indenture level to the highest is analyzed to determine the effects on
the system and to classify each potential failure mode in accordance
with the severity of its effect.

**Federal Geographic Data Committee (FGDC)** - Established by the Office
of Management and Budget for purposes of coordinating the development,
use, sharing and dissemination of geographic data.

**Field of View** -- The angular extent of the region from which a
sensor can collect data without changing position or orientation. This
can be applied to either the sensor as a whole or to individual
detectors in which case it is referred to as the instantaneous field of
view (IFOV).

**Focal Plane** -- The detectors and associated electronics assembled
with the spectral bandpass filters.

**Geodetic Reference System** - A comprehensive geodetic model of the
Earth that includes a geodetic reference frame, a best-fit Earth
ellipsoid/spheroid model, and an Earth gravitational model. The
inclusion of all these components allows a geodetic reference system to
serve as a horizontal and vertical datum. The standard LDCM geodetic
reference system is the World Geodetic System 1984 (WGS84).

**Ghost Image** - A ghost image is a secondary image of an object, which
appears as either an attenuated rendition of the original object or a
blurred and attenuated version of the original object. A ghost also has
a constant displacement vector from the original image. A significant
ghost is defined as an image artifact when its peak signal after
background level subtraction and radiometric calibration is above 2% of
the typical radiance (Ltypical) for that band.

**Ground Sample Distance (GSD)** - The distance on the ground between
adjacent detector sample centers.

**Housekeeping --** The engineering, health and safety, monitoring, and
diagnostic telemetry data that are used in the control and operations of
the observatory (spacecraft and image sensor(s)).

**Image Sensor Data -** The acquired science data whose characteristics
are specified in the LDCM Requirements Documents. Sensor data includes
calibration data that provides information on the instrument response to
dark images (dark calibration) and white images (lamp calibration) or
other external calibrations (solar, lunar, ground/ vicarious).

**Image-to-Image Co-registration --** Image-to-image co-registration is
defined as the difference in geolocation of images of the same WRS-2
path and row acquired at different times.

**Image Interval --** The period of time that the output from the image
sensor is either recorded or directly transmitted to the ground. An
image interval includes nominal, calibration and off-nadir pointing of
the imaging system.

**Imax -** The maximum response of an instrument as a polarizer analyzer
is rotated.

**Imin -** The minimum response of an instrument as a polarizer analyzer
is rotated.

**Inoperable Detector** - A detector that does not meet the definition
of operable detector (see **Operable Detector**).

**Inoperable Pixel -** A pixel is considered dead or inoperable if
greater than 50% of its ground projected area is not imaged by operable
detectors.

**In-Situ Calibration --** Sensor calibration data that provides
information on the instrument's response to dark images (dark
calibration) and white images (lamp calibration) for the reflective
bands. Sensor calibration data that provides information on the
instrument's response to known cold and hot sources (black-body
calibration sources) for the thermal bands.

**Jitter** - High frequency variations in sensor position and/or angular
orientation leading to deviations in the actual sensor line of sight
relative to the ideal line of sight over time periods up to a few
seconds. Jitter may be induced by mechanical vibrations from external
disturbances or internal mechanisms.

**LDCM Ground Network (LGN) --** The set of ground stations that are
used for routine mission operations in support of the LDCM. The stations
are located in Sioux Falls, South Dakota and Fairbanks, Alaska. A backup
site is located in TBD.

**Level 0 Data Product --** Level 0 data products are image data with
all data transmission and formatting artifacts removed, time provided,
spatial, and band-sequentially ordered multi-spectral digital image
data..

**Level 1G Data Products --** A Level 1G data product is any
geometrically corrected LDCM data product, such as Level 1Gs or Level
1Gt.

**Level 1Gs Data Products --** Level 1Gs data products consist of Level
1R data products resampled for registration to a cartographic
projection, referenced to the World Geodetic System 1984 (WGS84), G873
or current version.

**Level 1Gt Data Products --** Level 1Gt data products consist of Level
1R data products resampled for registration to a cartographic
projection, referenced to the WGS84, G873 or current version,
orthorectified, and corrected for terrain relief.

**Level 1R Data Products --**Level 1R data products consist of
radiometrically corrected image data derived from Level 0 data linearly
scaled to at-aperture spectral radiance.

**Lossless Compression --** A data compression process such that the
data, after compression and decompression, is identical numerically to
the data prior to compression.

**Measure** - Provide a value for a particular system parameter or
performance characteristic by direct observation

**Metadata --** A set of descriptive information about the scene data
contained in the archive. The information is sufficient for a user,
during the process of scene query and selection, to determine at a
minimum: geographic coverage, date of collection, sensor gain mode, time
of acquisition, cloud cover, and other qualitative measurements.

**Mission Data:** The data set containing LDCM imaging sensor data and
ancillary data.

**Mission Lifetime:** The LDCM Mission Lifetime starts at the NASA
acceptance of the LDCM Observatory and continues until the completion of
the Decommissioning Phase (The Observatory Design Life is defined in the
Space Segment Requirements Document).

**Mission Operations Center (MOC):** The facility used to coordinate
command and control the observatory for on-orbit operations. This
facility will be used during End to End testing of all elements of the
LDCM before launch.

**LDCM Phases:**

> **Storage Phase** begins after completion of the LDCM Observatory
> environmental test campaign and ends with the delivery of the
> observatory for final ground processing.
>
> **Pre-Launch Phase** begins after delivery of the LDCM Observatory to
> the launch site and ends at liftoff. This phase is divided into two
> sub-phases, the Observatory processing at the launch site before
> integration to the launch vehicle and the Observatory processing at
> the launch pad.
>
> **Launch and Early Orbit Phase** begins at lift-off and ends after the
> LDCM Observatory enters Safe Hold Mode and normal operations of the
> power and attitude control subsystems have been verified by the Flight
> Operations Team.
>
> Has completed all launch and early orbit activities and enter Safe
> Hold Mode.
>
> **Observatory Commissioning Phase** begins at the completion of the
> Launch and Early Orbit Phase and ends with acceptance by the NASA of
> the LDCM Observatory for the Operational Phase of the LDCM.
>
> **Operational Phase** begins at the completion of the Observatory
> Commissioning Phase and extends through the life of the LDCM
> Observatory.
>
> **Decommissioning Phase** begins after the end of the Operational
> Phase and extends through the necessary steps for the observatory to
> be compliant with the NPD 8710.3, NASA Policy for Limiting Orbital
> Debris Generation.

**Modulation Transfer Function Compensation (MTFC) Resampling** - The
modulation transfer function compensation resampling technique assigns a
value to each output (resampled) pixel, computed as a weighted
combination of the surrounding input pixels. The input pixel value
weights are computed based on the output pixel location relative to the
surrounding input pixels, using an interpolation function with a spatial
frequency response that has been designed to compensate for the spatial
frequency attenuation characteristics of the imaging system\'s
modulation transfer function.

**Nadir** - The direction from the Observatory towards the center of the
Earth. (See Reference: Space Mission Analysis and Design, Wiley J.
Larson and James R. Wertz, page 94, Second Edition -- 1992.)

**Narrowband Data** -- Observatory data down linked over a narrow band
width, typically S-band, which includes housekeeping data, tracking
data, commands and diagnostic telemetry. In addition, narrowband data
includes the commands, software updates and hard commands up linked to
the observatory.

**Near Infrared** - The spectral region covering 700-1000 nm.

**Non-uniformity Correction** -- Non-uniformity correction (NUC): The
process of performing a reversible on-board relative correction of gain
and offset for each pixel to reduce the entropy of a scene to improve
data compressibility and/or reduce errors in on-board aggregation or
resampling.

**Observatory --** The Observatory is defined as the satellite bus plus
any instrument(s) that are flown as part of the LDCM.

**Observatory Command Types:**

> **Relative Time Sequence -** commands that are required to be executed
> in a relative sequence to one another
>
> **Real Time** - commands executed upon receipt and acceptance by the
> observatory
>
> **Absolute** - commands that are to be executed at a specific time
>
> **Loads** - a set of commands that are stored and executed at a future
> time

**Off-nadir Image Intervals --** A continuous recording of LDCM image
sensor data or an LDCM data product not yet processed into a
185-km-(cross track) by 180-km (along track) multispectral image of the
earth surface where the original image data is derived from an off-nadir
observation.

**Operable Detector -** A detector is considered operable, even if out
of spec, when it meets the following requirements:

a.  The detector shall be sensitive to photons within its spectral band
    and not be saturated at expected operating temperatures under dark
    conditions.

b.  The detector\'s noise shall be less than 5 times the mean noise
    level for the band on which it occurs.

c.  The detector\'s dark current shall remain within +/- 5 times the RMS
    noise over the period between dark frame references.

d.  The detector\'s actual dynamic response range shall be greater than
    25% of the specified dynamic range; such that the Actual Dynamic
    Range \>= 0.25 \* Specified Dynamic Range.

**Optical Axes** - The X, Y, and Z axes of the Cartesian coordinate
system that aligns its positive Z-axis with the vector of the Optical
Axis of the telescope optical system traveling from the focal plane
towards the objective mirror of the telescope. The Optical Axes form a
right-handed coordinate system with the X-axis normal to the line formed
by the detectors in each band, and its positive direction is defined to
be towards the leading spectral band (the first band that images a
ground target object). The Y-axis is constructed as the cross product of
the Z-axis and the X-axis.

**Outgassing -** The emanation of volatile materials under vacuum
conditions resulting in a mass loss and/or material condensation on
nearby surfaces.

**Panchromatic Band** -- A broad spectral band colleted at a finer
Ground Sample Distance than other bands. Performance characteristics for
this band are defined in the LDCM Space Segment Requirements Document.

**Pixel** -- Short for "picture element", it is the smallest discrete
piece of image data in an image and corresponds to a single spatial
sample.

**Polarization Factor (PF)** - The modulation ratio PF =
(Imax-Imin)/(Imax+Imin) associated with a polarization sensitivity
measurement.

**Polarization Sensitivity** - The sensitivity of the system to changes
in the polarization of the signal.

**Priority Scenes --** Special image collection requests that are marked
by the observatory for priority data delivery, processed immediately
into Level 1 data products, and made available to the user.

**Priority Schedules --** Observatory command schedule uploads that are
developed, uploaded, and executed in an expedited fashion, i.e. outside
of the nominal schedule upload cycle.

**Reflective Band Sensor Data** -- Reflective Band Sensor Data are the
originally measured detector or detector column output counts at the
native spatial and spectral possibly adjusted by reversible offset and
scale corrections. Offset and scale correction reversibility implies
that the relationship between the original detector counts and the
remapped data counts is one-to-one for all measured detector output
values. See image sensor data.

**Relative Response** - Within the context of the specifications for the
LDCM Spectral Bands, the term Relative Response has the same definition
as the Relative Spectral Radiance Response Curve.

**Relative Spectral Radiance Response Curve** -- Is a normalized
(unitless) function of Spectral Radiometric Sensitivity divided by the
peak in-band Spectral Radiometric Sensitivity. The resultant data
plotted against wavelength generally appears to be a continuous smoothly
varying function or "curve". This is an instrument-level response (can
have a filter-level spectral response curve, too) that incorporates the
optical transmission of the telescope and optical bandpass filters, and
the photon detector's radiance responsivity.

**Scattered Light** - Undesired light contamination projected on a focal
plane caused primarily by uneven surface features on optical surfaces.
This optical surface roughness is usually measured by performing a BRDF
measurement for each optical surface.

**Scene --** A set of LDCM image sensor data, or an LDCM data product,
representing a 185-km-(cross track) by 180-km (along track)
multispectral image of the earth surface.

**Sensor Chip Assembly -** The smallest hardware unit of a focal plane
assembly/array.

**Sharpening Band** - Single spectral band that may have a finer spatial
resolution than the other bands, usually in an integer multiple, which
allows for sharpening of the multispectral bands.

**Signal-to-Noise-Ratio (SNR) -** The ratio of the level of the
information-bearing signal power to the level of the noise power. More
precisely, the signal-to-noise ratio of the mean digital number (DN) to
the standard deviation in DN. This is a temporal noise definition in
that the mean DN is the time averaged value and the standard deviation
in DN is the standard deviation in the time series.

**Software Criticality Classifications --**

(a) \"Mission Critical\" software is all software whose failure will
    cause permanent loss of the ability to successfully complete the
    minimum mission. Included in this classification are all LDCM Flight
    Software and firmware plus the ground software necessary to verify
    the correctness of the flight software (e.g., sensor, effector, and
    dynamics model software).

(b) \"Mission Support\" software is any software whose failure can
    impair any part of the mission. Recovery from failure of this class
    of software results in recovery of the functionality.

(c) \"Engineering Analysis\" software is software used in engineering
    analysis and simulations on an as-needed basis.

(d) \"Commercial\" software includes facility computer operating
    systems, software packages (e.g., mathematics packages, graphics
    packages), and high-level-language compilers employed in developing
    and maintaining software components.

**Software Types --**

(a) \"Developed\" software - This is all software developed in
    accordance with the full life cycle as defined in the Contractor\'s
    Software Development and Management Plan.

(b) \"Reuse\" software - This is any software that has been developed by
    previous projects which can be used in significant portions to
    reduce development cost or improve reliability of current projects.

(c) \"Heritage\" software - This is any Reuse software which has not
    only been previously developed, but which has been successfully
    flown (Flight Software Element), or successfully used for an
    equivalent Project (SDV Element).

(d) \"Off-the-Shelf (OTS)\" software - This includes any software
    purchased from a vendor including embedded run-time systems, data-
    base systems, mathematics and graphic packages, compilers, operating
    systems, etc.

**Off the Shelf Software --**

(a) Commercial-Off-the-Shelf (COTS) software - Software that is sold,
    leased, or licensed to the general public, either as a stand alone
    software product or embedded in a software system.

(b) Modified-Off-the-Shelf (MOTS) software - COTS software that is
    modified to meet unique requirements of a specific customer. This
    software requires ongoing unique maintenance for the life of the
    system not normally offered by the vendor.

(c) Government-Off-the-Shelf (GOTS) software - Software provided to the
    customer as GFE with no warranty or maintenance provided.

**Spectral Band** - An interval in the electromagnetic spectrum commonly
designated by a spectral bandwidth and a center wavelength.

**Spectral Band Center Wavelength** -- A wavelength within a spectral
band, halfway between the lower and upper band edges.

**Spectral Bandwidth** - The wavelength interval between the lower and
upper band edges. The lower band edge is the lowest wavelength where the
relative spectral radiance response is 50% of the peak response. The
upper band edge is the highest wavelength where the relative spectral
radiance response is 50% of the peak response.

**Stray Light** - Light scattered onto a detector from areas outside a
specified solid angle.

**Streaking Parameter -** The streaking parameter is defined by the
following equation:

$$Si\  = \ \left| \ Li\  - \ \frac{1}{2}\ (Li - 1\  + \ Li + 1)\  \right|\frac{\ }{\ }Li$$

where

L~i~ is the calibrated radiance value measured for a pixel at an input
radiance level;

L~i-1~ and L~i+1~ are similarly defined for the (i--1)^th^ and (i+1)^th^
pixels.

**Swath** - The strip on the Earth that the instrument observes as it
passes overhead.

**To Be Confirmed --** The term \"To Be Confirmed, (TBC)\" means the
requirement is subject to review for appropriateness and is subject to
revision. The resolution shall be made in coordination with the LDCM
Project Office.

**To Be Determined --** The term \"to be determined, (TBD)\" means that
no representative value/parameter has been identified for the
requirement. Requirement determination will be made in coordination with
the LDCM Project Office.

**To Be Resolved --** The term \"To Be Resolved, (TBR)\" means the
requirement has at lease two potentially conflicting values. A TBR is
subject to review for appropriateness and is subject to revision. The
resolution shall be made in coordination with the LDCM Project Office.

**Total-Ionizing Dose** -- a degradation mechanism in active electronic
devices resulting from trapping of charge generated by ionizing
radiation in the oxides of the device.

**Validation --** The term Validation is used in two distinct manners
within the LDCM requirements. Validation means to check and ensure that
the desired outcome is indeed the expected outcome of a requirement,
process or test. The second meaning is as an independent check of the
quality of the mission data to ensure that requirements are met.

**Verification:** The process of ensuring mission/segment requirements
are satisfied. Verification occurs using one or more of these methods :
analysis, test, demonstration, or inspection.

**Viewing Geometry --** The viewing geometry for which the data shall be
acquired, characterized by the zenith and azimuth angles from a ground
point to the sensor at the time of observation.

**Visible --** The spectral region covering 400-700 nm.

**Wideband Data --** The downlinked Mission Data combined with stored
housekeeping data that have been processed and formatted for efficient
data transmission.

> Examples of wideband data processing steps for LDCM purposes include
> lossless compression, error detection and correction coding, and
> pseudo-noise encoding. Examples of wideband data formatting include
> packet and frame-level organization of the LDCM image sensor,
> ancillary data and stored housekeeping data.

**World Geodetic System 1984 (WGS84) --** A global geodetic reference
system defined and maintained by the National Imagery and Mapping Agency
(NIMA). WGS84 is the standard geodetic reference system for LDCM. For
remote sensing applications such as LDCM, WGS84 can be considered to be
functionally equivalent to the International Terrestrial Reference
System (ITRS) and its International Terrestrial Reference Frame (ITRF)
realizations.

**World Reference System - 2** (WRS-2) -- A path/row coordinate system
used to define the ground tracks of the LDCM Observatory. The system
specifies latitudinal and longitudinal coordinates for image centers and
corners. In addition the WRS-2 assigns integer path (ground track) and
row designations to each image center. The corner points corresponding
to each path/row designation subtend a 185-km-by-180-km area on the
earth surface.

**WRS-2 Observation Period --** The period of time necessary to complete
a 16-day global repeat cycle

**WRS-2 Scene** -- The multi-spectral digital, image data acquired from
the LDCM Observatory, processed into a single image. The corner points
of a processed image correspond to a path/row designation that subtends
a 185-km (cross track) by 180-km (along track) area on the earth
surface. The original image data is derived from a nadir observation.

**Zenith** - The point in the celestial sphere that is exactly overhead.

**Zenith Angle** - The angle between the sun and the zenith for a given
position on the Earth\'s surface. Also, the complement of the angle
between the horizon and the sun (solar elevation).