The Earth Observer–March/April, 1995 Vol. 7, No. 2

Science Working Group for the AM Platform (SWAMP)

Philip Ardanuy (pardanuy@ltpmail.gsfc.nasa.gov), Research and Data Systems Corp.

 

The Science Working Group for the AM Platform (SWAMP) met at the Greenbelt Marriott on March 1-2, 1995. Representatives of every AM instrument team, as well as several other Earth Observing System (EOS) and platform scientists, were in attendance. Michael King presented an overview of the EOS Project. The various speakers then described instrument design, development, and testing progress. Issues affecting all instruments, and those overlapping certain instruments, were presented. Piers Sellers thanked those who attended the SWAMP for contributing to a successful meeting. The next “mini-SWAMP” meeting will be held at the EOS-IWG in Santa Fe in June, and there will be a “full-up” SWAMP somewhere on the East Coast in October 1995.

 

Project Science Office (PSO) Overview

 

King indicated that the Algorithm Theoretical Basis Document (ATBD) process has been more beneficial and difficult than originally envisioned. The Multiangle Imaging Spectroradiometer (MISR) group is the first science team to have all of its ATBDs delivered and online. Online access of every ATBD is the goal. Multiple formats in the delivered ATBDs complicated the process. The PSO is working to enhance the calibration and validation components of this program. Jim Butler is the new EOS Calibration Scientist. He spent last week in Japan calibrating the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Ocean Color and Temperature Scanner (OCTS) integrating spheres. Dave Starr is the new EOS Validation Scientist.

 

The next Investigator Working Group (IWG) meeting will be held June 27-29 in Santa Fe, NM. One half-day will be designated for breakout meetings on the EOS science plan. Part of the IWG will be devoted to reviews and discussions of these chapters.

 

AM-1 Overview

 

Chris Scolese reported that the spacecraft Critical Design Review (CDR) was completed successfully, along with the Headquarters external readiness review. In addition, the ASTER interface CDR, MISR CDR, and the Measurement of Pollution in the Troposphere (MOPITT) Interface CDR were completed during the past 4 months. These went very well, with no issues identified. The Clouds and the Earths Radiant Energy System (CERES) flight unit has been integrated and is in testing. The MODIS Engineering Model (EM) ambient testing is underway with very good instrument performance. Spacecraft subsystem EMs and life test units are progressing. Emphasis has shifted to completing instrument EM integration and spacecraft integration and test. The ASTER Thermal Infrared (TIR) is significantly behind schedule due to the pointing mechanism‹this is the greatest schedule concern at this time. Efforts are being made to advance the MISR delivery date to simplify spacecraft integration.

 

Current plans are to hold coordinated ASTER/MODIS/MISR Science Quarterly Management Reviews to foster the exchange of ideas. The reviews will look at algorithm development, calibration, validation, production processing software, science computing facility, and instrument operations. Covered are progress against plans, schedules, changes in scope, interfaces, and issues identification, with emphasis on schedule adherence. To reduce risks, Hughes no longer plans to move the Santa Barbara Research Center (SBRC) facility until after the first MODIS unit is delivered.

 

Following are the major AM project objectives at this time:

  • Deliver first CERES flight unit to TRMM (September 1, 1995)

 

  • Complete spacecraft design (April 1, 1995)

 

  • Complete testing of MODIS, ASTER, MISR, and MOPITT EMs (April 1, July 1, July 1, October 1, 1995, respectively)

 

  • Begin fabrication of instrument flight units for EOS AM-1 (prior to October, 1995)

 

  • Continue science software development towards beta delivery in the first quarter of FY96

 

  • Deliver launch vehicle test adapter to Lockheed Martin for Astro Space spacecraft modal survey (December 15, 1995)

 

  • Complete CAPL-2 flight on the Space Shuttle (prior to June 1995)

 

  • Resolve TRW solar array mounting, cost, and schedule concerns

 

  • Resolve ASTER scan mirror repointing disturbances

 

MODIS Instrument Status

 

Vince Salomonson reported that the Moderate Resolution Imaging Spectroradiometer (MODIS) EM is working at SBRC. Some data from the MODIS EM are being received at Goddard for analysis. The Team is working to reduce noise in the electronics to the 1 count level, and this has resulted in a 1-month schedule slip (which slack can accommodate). MODIS is feeling pretty good about progress to date. The dedicated MODIS test facility is in place at SBRC. Significant work remains on closing out the ATBDs, but rapid progress is being made. The Peer-Review Panel felt the atmosphere group was too small relative to the oceans group: the Announcement of Opportunity (AO) process will address this. Also, the Panel noted some duplication of products within MODIS, and a lack of connection with the MISR and CERES teams.

 

Software beta deliveries are in for 19 of 37 science products. By May 1, all but 5 product algorithms are expected to be in at Goddard. The Ocean Team will deliver the ocean algorithms as an integrated set. The beta delivery is more than a set of dummy modules, as the software creates and passes the planned parameters. But, scientifically, it is not the launch-ready algorithm set. The EOSDIS processing capacity (available MFLOPS) seems to be improved to largely meet MODIS needs, but networking and storage are still a concern.

 

CERES Instrument Status

 

Bruce Barkstrom presented the CERES status. The Tropical Rainfall Measuring Mission (TRMM) instrument copy is under fabrication, with calibration this Spring. Based on the peer review of calibration issues, the Team will try to improve ties to the National Institute of Standards and Technology (NIST), but must account for geometry and spectral output in the vacuum chamber and improve the coherence of the error budget.

 

ATBD revisions are being placed online (approximately 1,000 pages) as postscript versions. The team is aiming towards code delivery of “Release 1” for TRMM early in 1996. The Science Team is working through the algorithms and providing an operations concept for normal processing. Validation plans are to be discussed at the next CERES Science Team meeting (and are not accounted for by EOSDIS).

 

MISR Instrument Status

 

A MISR update was presented by Dave Diner. Average power, mass, and data rate of the EM are all well within allocation. The longest and shortest focal length lenses have been successfully assembled and tested–they meet or exceed all performance requirements. The charge-coupled devices’ (CCDs) performance and yields meet or surpass expectations. The pointing angles on the MISR optical bench are manufactured to better than required tolerances. Following extreme thermal cycling, angles returned to within <1 pixel deviation. The Primary Support Structure (PSS) was received from Loral (an aluminum honeycomb/graphite epoxy). MISR will decide whether to use the EM PSS for flight by May 1. The electronics are extremely quiet, with <1 digital count of noise at room temperature. One EM camera was put through and survived vibration testing.

 

The CDR was held December 1994, and MISR was assigned 17 action items and 4 advisories, and permission to proceed to the Protoflight Model (PFM) was granted. The MISR ATBD Peer Review was held May 11, 1994. The ATBDs were updated in December concentrating on reviewers’ responses, and a second update is expected in 1995. A Calibration Peer Review will be held March 27-28. The Science Data Processing System (SDPS) Beta System Design Review is scheduled for June 1995.

 

ASTER Instrument Status

 

Hiroyuki Fujisada made the ASTER presentation. ASTER is in the PFM design phase, with subsystem EMs finished with their development testing. The Shortwave Infrared (SWIR) and TIR boresight jitter due to cryocoolers show very small directly measured values (1ûarcsecond peak-to-peak for the SWIR subsystem and 0.6 for the TIR). Disturbance to other instruments from both cryocoolers will be very small. All ASTER system and subsystem CDRs were performed successfully. Allocation values in the Unique Instrument Interface Document (UIID) for ASTER are satisfied except for pointing. ASTER Ground Data System (GDS) contractors were selected in November 1994. The first interface meeting between the EOS Data and Information System (EOSDIS) and ASTER’s Ground Data System (GDS) is currently underway.

 

There are several issues for ASTER development. Pointing system EM delivery to the ASTER system was delayed. Delivery occurred on February 13. The TIR scanner pointing mechanism may affect instrument boresight jitter and stability. There are delays in the TIR scanner development.

 

Beta software version goals include the conversion of prototypes and specifications to production software. MODIS, MISR, and National Meteorological Center (NMC) interfaces have not been implemented. Hierarchical Data Format (HDF) is not used, Level 1 is dummied in, and error handling is not fully implemented. Beta software is proceeding on schedule for an April completion. The system will be integrated and delivered to the EROS Data Center (EDC) Distributed Active Archive Center (DAAC) in January 1996 as soon as the DAAC is ready.

 

MOPITT Instrument Status

 

The MOPITT presentation was made by Jim Drummond. Instrument Interface CDR was successfully held in mid-December. Module testing is in progress. The MOPITT calibration facility is being integrated and the EM is due in late April 1995. The CDR will be held on April 27, 1995. ATBD rewrites are beginning. Three members were added to the algorithm development team. A line-by-line model was replaced with an initial fast transmittance module, speeding up computations by 3 to 4 orders of magnitude. The retrieval was changed to a maximum likelihood method. MOPITT is using a 3-D chemical transport model to get initial a priori profiles and covariance matrices, which can be used, along with the Science Data Processing (SDP) Toolkit/AM Platform simulation data, to obtain MOPITT test data. The team is beginning to use the MODIS Airborne Simulator (MAS) to evaluate cloud detection and declouding approaches.

 

Integration and Testing (I&T)

 

The I&T Interface Control Document (ICD) is the key document detailing instrument provider and spacecraft provider plans, obligations, data, and activities. The focus for the coming year will be reconciling activity details, consolidating test data bases, and developing procedures. There is a preferred instrument integration order. Instrument performance will be checked regularly throughout spacecraft I&T via instrument-defined comprehensive performance tests. Once collected, instrument testing represents a continuous compatibility check. As feasible, instrument data collection and reduction should be maximized. Contamination control will be rigorously pursued during I&T. Spherical Integrating Source (SIS) testing is an integral component of the I&T process.

 

I&T issues extend across all aspects of instrument design, testing and operations, including Government-furnished equipment, data collection, data processing and archiving, limited life items, and environmental issues. Complete identification of instrument performance metrics is required to serve as a reference during I&T checks. In addition, external standards or targets, and system and/or subsystem compatibility are recommended standards for I&T. Additional I&T meetings are planned. The science community should be cognizant of I&T and focus on the resolution of inconsistencies. The project is looking at revising the integration schedule to install MISR first.

 

Lunar Calibration Issue

 

The issue of whether to configure the platform to permit instruments to view the moon for calibration purposes remains controversial. Engineering tradeoffs between the risks and thermal effects of periodic spacecraft maneuvering and the need for precision calibration differ for each instrument. Among the issues to be resolved are:

 

  • Benefits per se (space, moon)

 

  • Maneuver trajectories

 

  • Frequency of maneuver

 

  • Engineering considerations

 

  • Schedule and document delivery date

 

CERES has a critical requirement to view deep space limb-to-limb. The entire Earth Radiation Budget Experiment (ERBE) data set is pinned on two such space looks spaced about 2 years apart. This was performed to remove an instrument artifact in ERBE, and a similar effect is seen in CERES. MODIS has a similar requirement. Regardless of our knowledge of the lunar spectral albedo today, taking the lunar data will allow us, even 20 years from now should lunar knowledge improve, to go back and retroactively apply the improved knowledge to understand the observations. Hugh Kieffer is heading up a small team to write a white paper on the scientific and operational aspects of lunar calibrations. This report, assessing the maneuvers necessary to view deep space and the Moon, and the scientific benefits of such, will be presented at the next EOS IWG.

 

Gridding

 

The long debate over standard EOS-wide gridding schemes is hopefully almost over.

 

MISR data are intrinsically unregistered on the ground (by band by zenith angle). MISR uses a Space-Oblique Mercator (SOM) projection to develop a virtual MISR instrument for which all data are registered. To combine MODIS and MISR at Level 3, one may resample each to the International Satellite Cloud Climatology Project (ISCCP) grid. To merge MODIS and MISR at Level 2, a function is needed which resamples MODIS to the SOM grid. MISR and MODIS will coordinate this externally from the SWAMP. This issue will be resolved for the next SWAMP meeting.

 

Digital Elevation Model (DEM) Update

 

Martha Maiden reported that first priority is given to an initiative to produce a publicly available 1 km DEM. This builds on the existing Committee on Earth Observation Satellites (CEOS) øGlobeÓ program, which includes a Defense Mapping Agency (DMA) contribution, Digital Charts of the World (DCW) where available, National DEMs at 1 km by negotiation, supplemental gap filling, and a possibility of using satellite techniques. The second priority is 100 m global data. This expands on a MISR data access initiative. A joint Instrument Science/EOSDIS Working Group is being established to oversee implementation.

 

There is a proposed NASA/ESA project to develop DEMs using ERS SAR data and interferometric SAR techniques. Amazonia is a typical area with no DEM coverage, in part due to extensive cloud cover in that region. Satellite techniques (e.g., SAR) can be used to fill this in.

 

The plan is for processing system readiness by October 1995. Presently, JPL is prototyping the processing capability, including automation. The data will be freely available.

 

Ad Hoc Working Group on Production (AHWGP) Update

 

Bruce Barkstrom presented the EOSDIS data pyramid, which represents a hierarchy of increasing abstraction of data forms, from guide metadata to Level 0 data, that will all be available to the data users–this is a departure from the past strict demarcation of data versus metadata (see figure)

 

Validation Plans

 

A validation report is being prepared and integrated. Instrument team contributions should include prelaunch algorithm test/development requirements such as field experiments, operational surface networks, and existing data requirements. In addition, postlaunch requirements such as field campaigns, buoys, other satellite data, extensive data sets, and a common registration site, should be included. Instrument representatives for validation include: John Barker (MODIS), Tom Charlock (CERES), Jim Conel (MISR), Simon Hook (ASTER), and Laurie Rokke (MOPITT).

 

Sizing Issues

 

EOSDIS can meet the processing requirements, due in part to the phasing of processing loads and a decrease in the requirements. Capacity estimates are uncertain and estimates by instrument teams are based on current knowledge. A better understanding of built-in contingencies is needed, and the requirements must be validated by AHWGP. It is expected that capacity estimates will be reduced as software versions are implemented.

 

MODIS Test Data

 

Al Fleig and Steve Ungar addressed MODIS test data. MODIS contains 23 science team members, with more than 30 distinct products in three disciplines. Precursor test data types include Advanced Very High Resolution Radiometer (AVHRR), Coastal Zone Color Scanner (CZCS), High Resolution Infrared Sounder (HIRS), MAS, Thematic Mapper (TM), and soon the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). Test data can be modified instrument data resampled, rearranged, and reformatted. Test data can also be synthetically calculated rather than measured data. Uses of test data include algorithm development, algorithm transfer, algorithm and SDP toolkit integration, and SDPS resource usage and algorithm testing.

 

The MODIS Team Leader Computing Facility (TLCF) is producing synthetic data for geolocation based on available AVHRR and TM control points. The TLCF is creating synthetic data for algorithm transfer, integration, and operational testing.

 

CERES Test Data

 

The CERES Team is developing the test plan (tests and test data) to consider the following instrument and processing test issues: Is the instrument working properly and are we interpreting it properly? Can we create and read files? How good are our resource estimates? Can we handle exceptions? Do the algorithms produce good numbers? System testing will take place with Release 1 software. It will probably use the “best available” prelaunch data sets. CERES science testing uses 1 month of AVHRR/HIRS in conjunction with ERBE to wring out preliminary algorithms.

 

MISR Test Data

 

The MISR team discussed their test data. Test data are based on prototyping software; Advanced Solid-State Array Spectroradiometer (ASAS) data are also being used. Test data will come from MISR simulations, AVHRR, ASAS, Along-Track Scanning Radiometer (ATSR), AVIRIS, and Landsat. Initial testing is by subsystem, with each using the test data most appropriate. No data are passed between subsystems. The MISR-developed simulation program will be used to construct MISR data for end-to-end processing. Simulated data will be inserted into MISR packets and extended to full MISR granules. This will allow for a test of subsystem interfaces, and is intended to test software, not algorithms.

 

ASTER Test Data

 

ASTER test data development is underway. Algorithm developers provide files containing input simulated Level 1B radiance data, and expected results. Production staff add data dropouts, metadata, etc. The Japanese are developing three versions of Level 1 test data. The third will be complete at the end of 1995 and covers a full 60×60 km scene; it uses AVIRIS and Thermal Infrared Multispectral Scanner (TIMS) data.

 

MOPITT Test Data

 

Paul Bailey addressed MOPITT data simulation philosophy and realities. Spacecraft ground (thermal vacuum, etc.) data are virtually useless for testing production science software (beyond simple Level 0 ingest); they are not characteristic of Earth/atmosphere scenes. Each production processing step has its own unique pathological scenarios, with Level 1 not the same as Levels 2 or 3. Also, different processing steps need different quantities of input data for verification. “End-to-end” testing leads to a very complex simulator if all pathological conditions are to be modeled into Level 0. The simulator software becomes as complicated as the production software. This is difficult to verify and expensive to build.

 

It is most cost effective to build separate simulators for each data level that models the pathological problems for the next software level. Testing verifies the data interfaces, input and output. Benign simulations are used to verify flow between the processing steps.

 

With respect to beta delivery, MOPITT will deliver all test data including ancillary data necessary to run Science Data Processing (SDP) software. The DAAC must be able to make this ancillary data available in an “operational” context. For MISR Version 1 delivery, it is anticipated that the DAAC ingest data from ancillary sources corresponding to agreed-upon scenarios. MOPITT would use the same source of ancillary data in creation of simulated data sets. Version 2 delivery is handled the same as Version 1, but extended to a wider range of scenarios, possibly using the MODIS test set as a source of cloud data, etc. Ancillary data required includes temperature (including surface) and moisture at standard levels, and DEM as supplied by SDP toolkit.

 

ESDIS Update and Beta Deliveries

 

Steve Kempler addressed the current ESDIS status. Current AM instrument science software deliverables include:

 

1 Beta (interface and initial sizing) delivery between September, 1995 and March, 1996

 

2 Version 1 (engineering delivery) between June, 1996 and December, 1996

 

3 Version 2 (science delivery) between July, 1997 and January, 1998

 

4 One additional “delta” delivery allowed per team between Version 2 and launch

 

A symmetric multiprocessing (SMP) class of hardware platforms has been selected. The SDP Toolkit TK4 was delivered February 28, 1995. There is a minimal impact on efficiency for TK4 delivered functions (this is about 80 percent of the toolkit). TK5 will be delivered July 95 and will contain process control, metadata access, status message, and prototype EOS Hierarchial Data Format (HDF) tools. The selection and procurement of a graphics package is due in March.

 

There will be a Science Software Integration and Test (SSIT) Workshop to bring together instrument teams and DAAC personnel to better understand the SSIT process, delineate roles, and begin developing documented agreements.

 

Requirement for “Rapid-View” Data

 

Quick-look went away during downsizing. This included Level 0 data, as well as Levels 2 and 3. ASTER was most affected due to the shipping delays, but instrument teams all require some mechanism for anomaly resolution, etc. From a spacecraft point of view, this need can be satisfied. ESDIS also is able to meet the need using “rapid-view” data, with no impact to costs, if this is worked in a less formal way than leveling requirements.

 

The need for such rapid view has been born out in recent missions, such as the Upper Atmosphere Research Satellite (UARS). For example, since September 1991, 299 of the 300 crashes of the Solar Stellar Irradiance Comparison Experiment (SOLSTICE) instrument were recovered viewing the near-real-time data, including about 30 events overlooked by the Flight Operations Team (FOT). UARS demonstrated that regular AM Project access to near-real-time data will provide early detection of instrument anomalies and reduce the resulting loss of data.

 

The goal is to provide a viable approach for expediting preprocessed science data to users for the purposes of instrument activation, calibration, anomaly resolution, and rapid scientific evaluation. The solution is to make expedited data sets available to users from the DAACs within a nominal 2 to 3 hours after receipt. This would be a small subset in addition to the normal full Level-0 processed data stream.

 

Ancillary Data Update

 

Matthew Schwaller addressed the policy regarding ancillary data acquisition. External data sets are those of interest to Mission to Planet Earth (MTPE) activities, generated by non-NASA agencies, that may or may not reside at EOSDIS DAACs. There are three types:

 

1 Required for product generation

 

2 Required for validation, calibration, and algorithm development

 

3 Required for research

 

Generally, in cases (1) and (2), EOSDIS will assume all responsibility for providing data access. In other cases, for example, where non-production data are required by one or a few investigators, more responsibility will fall on the investigators. The number and volume of external data sets needed for EOS standard product generation must be well-defined. Significant access issues exist. EOSDIS will generally not fund the acquisition of datasets which do not now exist. Needs must be explicitly expressed so research for the best means to acquire data may begin.

 

 

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