About

Last Update: Jan 5, 2007

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 July 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 Collection 4 L1, land, and atmospheres products from the forward processing chain. The atmospheres Principal Investigators are in the process of developing Collection 5 atmospheres and land codes. This process has been completed for Aqua atmospheres codes and will be completed for Terra in July 2006. The Collection 5 Terra land codes will be available in early-June 2006 and the Aqua codes will be available in September 2006. The Collection 5 L1 codes have already been developed for Collection 5. MODAPS is in the process of converting its forward processing activity from Collection 4 to Collection 5. The schedule for this is as follows:

• Collection 4 Aqua and Terra L1 and cloud mask products will be generated until September 2006.
• There will considerable overlap between the production of Collection 4 and Collection 5 L1 and cloud mask products because of the timing in the availability of the land and atmospheres L2+ codes and the transition of GES DAAC functionality to MODAPS. The generation of Collection 5 Aqua L1 and cloud mask products has already started and the production of Terra products will start in early-June 2006.
• The generation of Collection 4 atmospheres and land products is driven by the availability of the Collection 5 codes. Further there will be overlap of Collection 4 and Collection 5 atmospheres products as a result of the transition of the GES DAAC functionality to MODAPS.
• The Aqua Collection 4 atmospheres products will be generated until the end of May 2006. The production of Collection 5 products started in April 2006.
• The Terra Collection 4 atmospheres products will be generated until the end of July 2006 and perhaps beyond. The production of Collection 5 products will start in early-July 2006.
• The Aqua and Terra Collection 4 land products will be generated until mid-September 2006 when the production of Collection 5 products will commence.

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 atmospheres Aqua codes has been completed and development of the land Terra codes will be completed shortly (early June). The atmospheres Terra and land Aqua codes will be developed by July and September 2006 respectively. The Collection 5 reprocessing will involve the generation of approximately 10 years of data products. The reprocessing will proceed according to the following schedule:

• The atmospheres Aqua Collection 5 reprocessing started in early April 2006. This reprocessing will be completed, from first light until the time that the Collection 5 forward processing started, by early-July 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 a rate of 15 datadays/day (referenced as 15x).
• The atmospheres Terra Collection 5 reprocessing will start in early July and will be completed by mid-December 2006. As with Aqua, this reprocessing will be performed out of time order.
• The land reprocessing will start in early June at Terra first light. The Terra-only interval (i.e. through July 4, 2002) will be completed by mid-January 2007. Due to the large number of science codes and the large data volumes compared to atmospheres, this reprocessing will proceed at approximately 3.6x. Starting in mid-January, Aqua and Terra will be reprocessed in parallel to expedite the generation of the land-combined products (i.e. products requiring both Terra and Aqua data). The land Collection 5 reprocessing will be completed in 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 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 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 atmospheres and land L2+ data products. The atmospheres and land L2+ products continue to be exported to the GES DAAC and the LP DAAC/NSIDC DAAC respectively. The GES DAAC continues to be the principal archive for the atmospheres data products. However, the Collection 4 atmospheres L3 data products are also archived by MODAPS in LAADS.
• MODAPS does not archive any Collection 4 L1 data products in LAADS. Further, the GES DAAC stopped Collection 4 L1 data production for Terra and Aqua at dataday February 24, 2006 and, therefore, does not archive Collection 4 L1 products beyond this date.
• MODAPS has started reprocessing production for Aqua Collection 5 L1 and atmospheres data products and archives these in LAADS and the associated data pool according to the scheme identified above. The GES DAAC does not archive any Collection 5 atmosphere data products.
• The GES DAAC continues to generate and archive Collection 5 L1 and cloud mask Aqua and Terra data products. Aqua product generation and archive will cease very shortly (early June)

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 the Level 1 and Atmospheres Archive and Distribution System (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:9400/ 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 ladssci.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@sigmaspace.com or Barbara DeShong at barbara.deshong@sigmaspace.com. 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 and OpeNDAP 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 (the following situation is written on the assumption that the LAADS has been opened to the general user community):

• Aqua and Terra L0 data products are available on a special request basis by contacting User Services at modapsuso@sigmaspace.com.
• Aqua Collection 5 L1 data products are available through LAADS but only for that portion of the Aqua interval that has been reprocessed. These products are not available through the GES DAAC.
• Terra Collection 5 L1 data products are available from the GES DAAC through EDG but only for that portion of the Aqua interval that has been reprocessed.
• 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@sigmaspace.com.
• Aqua Collection 5 atmospheres products are available from LAADS but only for that portion of the Aqua interval that has been reprocessed. These products are not available from the GES DAAC. No Terra Collection 5 data products are currently available.
• 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 Collection 5 atmospheres production and Aqua and Terra Collection 4 atmospheres and land forward production. The GES DAAC is providing L1 subscription services for Terra Collection 5 L1 data products (including cloud mask/profiles).
• 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 Dr. Michael Teague at michael.teague@sigmaspace.com.

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@sigmaspace.com. User Services also maintains a toll-free (U.S. only) number: 1-866-506-6347. 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.