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MODIS Web Organigram

The Level 1B Software
System Overview

Contents of Level 1B Software System Overview

Introduction
Requirements
Functionality
Data Input and Output
Data Interfaces
Top-Level Architecture
Flow Chart to Top-Level Architecture
Performance Metrics

Introduction

  • The MODIS Level 1B in-granule software is being developed to implement the calibration algorithms for the reflective and emissive bands. The software is being developed in accordance with the Software Engineering Institute (SEI) Level 2+ standards.

Requirements

  • The software meets the requirements documented in the MODIS Level 1B Software Requirements Specification and derived from:
    • the Team Leader Working Agreement (TLWA),
    • the EOSDIS Core System (ECS), and
    • the MODIS Science Team.

Functionality

  • The level 1B software transforms raw science data, organized into five minute granules by the level 1A software system, into calibrated data products.
Schematic showing data flow from S/C through L0, L1A, L1B, L2 and higher-level processing
  • Specifically, the level 1B software performs the following functions:
    • Corrects raw detector counts sent to the ground for the following effects:
      • Electronic offsets
      • Instrument self-radiation
      • Effect of temperature variations of the instrument on detector response
      • Scan angle variations
    • Transforms the corrected digital signals to calibrated radiance and reflectance products.
    • Calculates the uncertainties in the calibrated products.
    • Transforms engineering data to scientific data
    • Performs quality assurance on the calibrated data. This includes reporting quantities such as the percentage of saturated data per band, reporting noise in temperature measures, etc.
    • Reports instrument status information; e.g. whether the instrument is undergoing a maneuver.

Data Input and Output

Inputs:

  • Uncalibrated DNs, metadata, etc. from PGE01
  • Geolocation file from PGE01
  • Reflective Solar Bands Lookup Tables
  • Thermal Emissive Bands Lookup Tables
  • Quality Assurance Lookup Tables

Outputs:

  • Earth-view data: Corrected digital signals for reflected solar bands, and coefficients to convert them to radiances and reflectances and radiances for thermal emissive bands. Separate output files are written for:
    • 250m resolution bands
    • 500m resolution bands (with 250m bands aggregated to 500m)
    • 1km resolution bands (with 250m and 500m bands aggregated to 1km).
  • On-board cal (OBC) Raw Data for
    • Black-body (BB)
    • space-view (SV)
    • spectroradiometric calibration assembly (SRCA)
    • solar diffuser (SD)
    • engineering data
    • metadata needed to support analysis of calibration sector data.

Data Interfaces

Schematic showing PGE02 data interfaces (inputs & outputs)

Top-level Architecture

  • The architecture of this system has been developed to accommodate the evolution of the calibration algorithm which is taking place as MCST's understanding of the instrument grows, and as changes occur in the instrument's performance on-orbit. The software design also accommodates corrections determined from external sources of data such as other satellite instruments, airborne sensors, and ground based instrumentation.

Flow chart to Illustrate Top-level Architecture

Flow chart of Level 1B top-level architecture

Performance Metrics

  • These performance metrics apply to version 2.3.0 (delivered December 14, 1999).
Table of Level 1B performance metrics

Responsible Civil Servant: 
Dr. Jack Xiong <Xiaoxiong.Xiong.1@gsfc.nasa.gov>

Email mcst-webm@ssaihq.com to report any problem with the MCST Web Pages.

Last Update:  July 3, 2008

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