LANCE-MODIS operates on a 7x24 hour basis. LANCE-MODIS has two
standalone systems that use different network routes. It is expected
that this redundancy will reduce the system downtime to less than 1%.
Whereas the standard MODIS forward processing acquires 2-hour L0 files for
Aqua and Terra from EDOS within 7-8 hours of real time, LANCE-MODIS
acquires session-based L0 files from EDOS and the end of the session is
available within 10-30 minutes after real time. LANCE-MODIS uses the
Terra attitude and ephemeris data entrained in the L0 data. However, for
Aqua the attitude and ephemeris data are acquired from the EDOS rate
buffer. LANCE-MODIS acquires all of the ancillary
products from the data suppliers. The production rules for some of the
science codes have been relaxed with respect to these ancillary data to
allow the data products to be generated within 3 hours of real time.
All of the MODIS Level 1 (L1), L2, and L3 products generated by
LANCE-MODIS have been modified to add "NRT" metadata to the filenames to
enable the products to be distinguished from the MODIS standard
forward-processed products. In addition, Digital Object Identifier (DOI)
metadata has been added to all the Terra and Aqua MODIS NRT products.
Data products are archived in a rolling archive for 7+ days and are
available for distribution by direct access to the
Clarification of differences that distinguish MODIS NRT products:
Differences between Terra and Aqua MODIS NRT versus their standard products
Terra MODIS NRT products are generated using predictive ephemeris and attitude data for satellite position (from NASA's Flight Dynamics Facility (FDF)), whereas the Terra MODIS standard products use the embedded definitive ephemeris and attitude data for navigation purposes. Aqua MODIS NRT products are also based on predictive ephemeris and attitude data. The Aqua sensor (unlike Terra) lacks the ability to generate definitive ephemeris and attitude data, and therefore, the FDF calculates predicted satellite ephemeris data and uploads it to the spacecraft once per day. This data is later returned to the ground stations as Ground-Based Attitude Determination (GBAD) data, which is also time-coordinated with the other instruments. This GBAD ephemeris and attitude data is used to process Aqua MODIS standard products.
Relaxed ancillary data requirements
The production rules specific to ancillary data requirements were relaxed for some of the Level 2 product generation codes (L2 Clouds, Cloud Mask/Profiles).
Level 2 Land Surface Reflectance product
The L2 Land Surface Reflectance product's Principal Investigator developed a special version of it for NRT applications. This product uses the National Oceanic and Atmospheric Administration's (NOAA) Global Forecast System (GFS) ancillary product; the standard product uses the Global Data Assimilation System (GDAS) input.
Differences between MODIS C5 and C6 NRT products
Apart from the above description of the differences between the NRT and standard products, users should remain cognizant of qualitative improvements and changes in C6 standard MODIS land and atmosphere products. Such improvements and changes naturally carry over to their NRT product counterparts as well.