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About

Last Update: December 23, 2010

The purpose of this page is to provide users of the MODAPS/LAADS with a variety of basic information concerning the MODIS instrument, the MODIS products, and the services available from MODAPS for the acquisition of MODIS products and production codes. As noted on the home page, the transition of the GES DAAC MODIS production and distribution functionality to MODAPS results in the fact that the MODAPS services will change over the period from the present through September 2006. At the end of the transition MODAPS will be the location for all production of MODIS atmospheres and L1 data products, and all archive and distribution of MODIS L0, Collection 4 and 5 atmospheres, and L1 data products.

Details of the transition are provided at Transition Issues and Transitions Planned and Transition Completed.

The MODIS Instrument

Details concerning the Aqua and Terra MODIS instruments are available at MODIS Technical Specifications (this link will open in a new browser window).

Using the MODIS Data products

Information concerning the MODIS data products and their use is available at Terra Product Descriptions and Aqua Product Descriptions

Improvements from Collection 4 to Collection 5

The development of the Collection 5 L1 and atmospheres codes from their predecessor Collection 4 codes has been a 2-year development and test process. The changes and improvements incorporated into the Collection 5 codes are quite considerable. Improvements in the L1 and cloud mask codes are identified in MODIS Collection 5 Improvements Summary and improvements in the atmospheres codes are discussed in MODIS Atmospheres Collection 5 Update (this link will open in a new browser window).

The MODIS Vocabulary

As any complex science instrument and data system, MODIS utilizes and has developed its own special vocabulary. Explanations of the terminology used throughout this web site are given in MODIS Nomenclature.

MODAPS Production

Forward Processing

The MODAPS generates Aqua and Terra L1, atmospheres, and land data products on a near-real time basis using L0, ancillary, and ephemeris and attitude data products obtained from the GES DAAC. On this web site, this is referenced as forward processing. Because of latency in the supply of data products from the ancillary data providers, MODAPS is able to generate forward processed L1 and L2 atmospheres products approximately 24 hours behind real time. In August 2006, MODAPS will interface directly with EDOS and will obtain L0 data from this source rather than the GES DAAC.

At the present time MODAPS generates forward-processed Collection 4 L1 and land products and Collection 5 L1 and atmospheres products for Aqua and Terra. The land Science Team is still science testing the Aqua algorithms and the Collection 4 land processing will not be converted to Collection 5 until this is completed. It is expected that this science testing will continue until late December 2006 and the Collection 5 conversion will be made on dataday January 1, 2007.

Reprocessing

As new Collections of atmospheres and land codes become available, MODAPS reprocesses all L1 and L2+ data products from first light of Terra and Aqua to the present time. Terra first light occurred on February 24, 2000 and Aqua first light occurred on July 4, 2002. For the past 2 years the Principal Investigators have been developing the Collection 5 science codes. Development of the Collection 5 atmospheres Aqua and Terra codes and the land Terra codes has been completed. The Collection 5 land Aqua codes will be available in late December, 2006. The Collection 5 reprocessing will involve the generation of approximately 10 years of data products. The reprocessing schedule is as follows:

  • The Collection 5 Aqua atmospheres reprocessing stared in early April 2006 and was completed in mid-July.
  • The Collection 5 Terra atmospheres reprocessing was started in mid-July and will be completed in mid-December, 2006. The reprocessing is being performed out of time order in order to provide end-user continuity as the GES DAAC functionality transfers to MODAPS. The reprocessing is being performed at 15 datadays/day (referenced as 15x).
  • The Collection 5 Terra land reprocessing started in mid-July and started at first light. The reprocessing will proceed at approximately 3.5x and the Terra-only interval (i.e. through dataday July 4, 2002) will be completed by late-February 2007. Thereafter, Aqua and Terra will be reprocessed in parallel to expedite the generation of the land combined products (i.e. those products requiring both Terra and Aqua data). The land reprocessing will be completed by late April 2008.

Additional details of the MODAPS data production (planned and actual production, ingest metrics, versions of science codes used in production, etc.) are given at Production and details of the reprocessing plans are provided at Collection 5 Atmospheres Reprocessing Plan and Collection 5 Land Reprocessing Plan.

Ordering MODIS Data Products from MODAPS and LAADS

Data Archive

Historically, MODAPS has exported forward processed and reprocessed atmospheres and land data products to the GES DAAC and the LP DAAC/NSIDC DAAC respectively. These DAACs have been responsible for subsequent distribution to the end user community. Further, the GES DAAC has had the responsibility for generating and distributing to end users the L1 and cloud mask data products although MODAPS has also generated these products in the course of its production from L0 data. In addition, the GES DAAC has been responsible for acquiring the ancillary and ephemeris/attitude products and providing these to MODAPS to support their production efforts. The DAACs have used the EOS Data Gateway (EDG) as a mechanism for exporting data products to the end user community.

The present transition of MODIS functionality from the GES DAAC to MODAPS will not affect the export of land data products to the LP DAAC/NSIDC DAAC for subsequent distribution to end users. The Collection 4 and 5 product generation referenced above will continue to lead to MODAPS product export to these DAACs.

At the end point of the GES DAAC/MODAPS transition in September the following situation will prevail:

  • MODAPS will provide the principal archive for MODIS L0 data and MODAPS will acquire these data from EDOS. These data will be maintained on disk. The present archive is approximately 200TB in size and will grow at a rate of 3TB/month. The backup will be the EDOS archive maintained at White Sands in tape form.
  • The GES DAAC will continue to be responsible for the acquisition of ancillary, ephemeris, and attitude data products and for providing these to the MODAPS. However, MODAPS will archive all ancillary data in the Level 1 and Atmosphere Archive and Distribution System (LAADS) and will provide distribution services for these from this system.
  • Collection 5 L1 and cloud mask products will be generated and archived solely by MODAPS. All Collection 5 geolocation and cloud mask/profiles data products will be archived on disk in LAADS in compressed form for subsequent distribution to end users. Some Collection 5 L1B products will be archived in LAADS in compressed form. These correspond to the continental U.S., Western Europe, and Southern Asia geographic regions. The remaining L1B products will be archived in compressed form in a "rolling" data pool that will have a capacity of approximately 25 production days (400 datadays). This data pool will be accessible by end users through LAADS. MODAPS will not archive any Collection 5 L1A data products or any L1 data products for Collection 4.
  • All MODAPS production activities for land and atmospheres L2+ products will be for Collection 5. MODAPS will archive all atmospheres Collection 5 data including cloud mask/profiles and browse products on disk in LAADS in compressed form for subsequent distribution to end users. MODAPS will also archive Collection 4 L2+ atmospheres data products in LAADS in compressed form. Further, LAADS will archive the so-called "golden month" atmospheres data products for all earlier Collections. Certain land products have been identified by the atmospheres community as being required to support atmospheres analyses. At the present time these are limited to albedo data products that will be archived in LAADS from the Collection 5 land reprocessing.
  • MODAPS will export all Collection 5 land products to the LP DAAC/NSIDC DAAC for subsequent distribution to end users.

As noted, some of the archive items listed above are in a state of transition from the GES DAAC to MODAPS. At present, the following situation prevails:

  • MODAPS continues to produce Aqua and Terra Collection 4 L1 and land products and the latter continue to be exported to the LP and NSIDC DAACs.
  • MODAPS does not archive any Collection 4 L1 data products. Further the GES DAAC stopped Collection 4 L1 data production on February 24, 2006.
  • MODAPS does not yet have a complete atmospheres L2 Collection 4 archive and is in the process of transferring these data from the GES DAAC. Until this is completed later this year, the GES DAAC remains the archive for the L2 data. MODAPS has a complete archive of the atmospheres L3 data products.
  • MODAPS has a complete archive for the Aqua Collection 5 atmospheres products a partial archive for the Terra products (see Reprocessing above). The Aqua and Terra L1 products are being archived at MODAPS/LAADS using the approach identified above. The GES DAAC is no longer distributing Aqua L1 products but will continue to distribute Terra L1 products until these are available from MODAPS.

Additional details of the MODAPS data archive are at given at Atmospheres Archive and at Atmospheres Archive Table and access instructions are provided at Data Access. The Data Availability page provides a detailed identification of the data products presently archived in LAADS.

Data Distribution

MODAPS will utilize LAADS to distribute Level 1 and atmospheres data products archived in this system as defined above. LAADS may be found at http://ladsweb.nascom.nasa.gov/ and this system may be used to access any data products archived in the permanent archive or L1B data products temporarily archived in the rolling data pool as defined above. Any requests from end users for L1B data products outside of the interval contained in the data pool will be automatically processed by LAADS on a processing-on-demand (POD) basis. Data may be retrieved from the LAADS/data pool archives by direct access through anonymous FTP. The FTP site is ladsweb.nascom.nasa.gov. Further details of these access approaches are given in Data Access.

Even under heavy load, LAADS is designed to perform searches and orders in seconds except in circumstances in which POD or post-processing is performed. In contrast to the EDG and the GES DAAC WHOM delivery systems, LAADS includes a wide variety of post processing capabilities that have been included in direct response to requests from the atmospheres user community. These include metadata searches, recurring temporal searches, geographic sub-setting, parameter sub-setting, sub-sampling, masking, mosaicing, reprojection, and GeoTIFF parameter conversion. Details of the capabilities of the current and future versions of LAADS are given at LAADS Capabilities.

MODAPS provides subscription services that provide individual users and groups of users with data products at the time of their production. These products are normally pushed to users but data products may also be added to the data pool for subsequent data pull by end users. These subscriptions may include limiting data products by geographic region. MODAPS also accepts special user algorithms that can be incorporated into the production activity as algorithm codes (referenced as Sub-setters) that generate special products for user distribution through subscriptions. Subscriptions and Sub-setters may be applied to both forward and reprocessing production activities. Requests for subscriptions and sub-setters should be sent to User Services at MODAPSUSO@lists.nasa.gov. MODAPS also process special ad hoc user requests (e.g. requests for historical L1A data products) that should also sent to User Services.

At the completion of the GES DAAC/MODAPS transition process in September 2006, the following data products will be distributed by MODAPS to the general user community:

  • Aqua and Terra L0 data products. Small volumes of data will be provided through LAADS. Bulk distributions will be made through direct access to the L0 archive.
  • Aqua and Terra Collection 5 L1 data products will be provided through LAADS. User requests for Collection 4 L1 data products will be processed by MODAPS as ad hoc requests.
  • Aqua and Terra Collection 5 atmospheres data products (including cloud mask/profiles) and certain land products (albedo) will be available through LAADS.
  • Aqua and Terra Collection 4 atmospheres data products (including cloud mask/profiles) and golden month data products for earlier Collections will be available through LAADS.
  • Aqua and Terra Collection 5 land data products will be exported by MODAPS to the LP DAAC and the NSDIC DAAC for subsequent distribution to the general user community.
  • Subscription and Sub-setter services will be provided for all Aqua and Terra Collection 5 atmospheres and land data products generated by forward and reprocessing production activities.
  • MODAPS will provide metadata and browse for L1 and atmospheres data products archived in LAADS/data pool to the Earth Observing System Clearing House (ECHO). Cross-DAAC data searches will be conducted using the Warehouse Inventory Search Tool (WIST) and LAADS will be capable of responding to data requests from that source.
  • LAADS will support McIDAS users.
  • None of the above products will be available through the GES DAAC.

As noted, some of the distribution items listed above are in a state of transition from the GES DAAC to MODAPS. At present, the prevailing situation is:

  • Aqua and Terra L0 data products are available on a special request basis by contacting User Services at MODAPSUSO@lists.nasa.gov.
  • Aqua and some Terra Collection 5 L1 data products are available through LAADS. These products are not available through the GES DAAC.
  • Terra Collection 5 L1 data products are available from the GES DAAC through EDG.
  • Aqua and Terra Collection 4 L1 data products are available from the GES DAAC for the time interval ending February 24, 2006. Requests for later data should be submitted to MODAPS User Services at MODAPSUSO@lists.nasa.gov.
  • Aqua and some Terra Collection 5 atmospheres products are available from LAADS. These products are not available from the GES DAAC.
  • Aqua and Terra Collection 4 L3 data products are available from LAADS. These products and the L2 data products are available from the GES DAAC.
  • The Golden Month data products for Collection 4 and earlier Collections are available through the GES DAAC.
  • MODAPS is providing Subscription and Sub-setter services for Aqua and Terra Collection 5 atmospheres reprocessing production and Aqua and Terra Collection 4 atmospheres and land forward production. MODAPS is providing these services for L1 Aqua and Terra forward processing. The GES DAAC continues for Terra reprocessing.
  • MODAPS is exporting Collection atmospheres and L1 metadata and browse products to ECHO.
  • MODAPS supports McIDAS users.

The authors appreciate that the transition process is confusing for end users and reiterates that the comprehensive nature of the GES DAAC services dictates that the transition should be a gradual process spanning over a 6-month time period. Please submit any questions to Gang Ye at Gang.Ye-1@nasa.gov.

User Services, Frequently Asked Questions, and Quality Assurance

MODAPS operates a User Services group which includes both logistics/delivery system and science support. The former acts as a single point-of-contact for all user requests. The contact point is MODAPSUSO@lists.nasa.gov. User Services also maintains a toll-free (U.S. only) number: 1-800-596-8132. The hours of operation are 9 a.m. to 5 p.m. EST Monday through Friday. Requests for support through e-mail or the voice recording service are monitored outside of these hours and response will be made to urgent requests outside of the standard hours. Science support is provided by Bill Ridgway at 301-614-6215 or Bill.Ridgway@nasa.gov. Additional details concerning User Services are given at User Services.

MODAPS maintains a list of frequently asked questions that is updated frequently. These may be found at Frequently Asked Questions.

The atmospheres Quality Assurance site is currently being developed.


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