AMSR-E LANCE Frequently Asked Questions

►  What is AMSR-E?
►  What is LANCE?
►  What is the AMSR-E SIPS?
►  What is the relationship between the SIPS and the GHRC DAAC?
►  What AMSR-E products are available?
►  How do I access near real-time (NRT) AMSR-E data products from the AMSR-E SIPS?
►  Is User Registration required to get the LANCE data? How do I register?
►  Can I subscribe to an RSS feed for the NRT AMSR-E data products?
►  What is the cost of the data?
►  How long are the data available on line? What if I want older data?
►  What are the differences between the LANCE products and the standard products?
►  What is the NRT data latency?
►  Why should I use standard products instead of NRT products?
►  Where do I get Standard Products? What is the latency?
►  What format are the data in?
►  Is the data quality controlled?
►  What do the various product levels represent?
►  How are NRT products distinguished from standard products?
►  What are "P" files?
►  How do I cite the data?
►  Whom do I contact for more information?
►  Is documentation available?
►  Can the data be subsetted?
►  Are browse data available?
►  Can I get a data subscription?

What is AMSR-E?

The Advanced Microwave Scanning Radiometer - EOS (AMSR-E) is a conically scanning passive microwave radiometer sensing microwave radiation at 12 channels and 6 frequencies ranging from 6.9 to 89.0 GHz. The instrument (AMSR-E) was developed and provided by NASDA, now known as JAXA, with close collaboration between U.S. and Japanese scientists. Horizontally and vertically polarized radiations are measured separately at each frequency.

The AMSR-E instrument, modified from the design used for the ADEOS-II AMSR, utilizes an offset parabolic reflector 1.6 meters in diameter to focus the radiation into an array of six feedhorns. The feedhorns feed the radiation to the detectors. The reflector and feedhorn arrays are mounted on a drum that contains the radiometers, digital data subsystem, mechanical scanning subsystem, and power subsystem. The reflector/feed/drum assembly is rotated about the axis of the drum by a coaxially mounted bearing and power transfer assembly. All data, commands, timing and telemetry signals, and power pass through the assembly on slip ring connectors to the rotating assembly.

A cold load reflector and a warm load are mounted on the transfer assembly shaft and do not rotate with the drum assembly. They are positioned off axis such that they pass between the feedhorn array and the parabolic reflector, occulting it once each scan. The cold load reflector reflects cold sky radiation into the feedhorn array thus serving, along with the warm load, as calibration references for the AMSR-E. Calibration of the radiometers is essential for collection of useful data. Corrections for spillover and antenna pattern effects are incorporated in the data processing algorithms.

The AMSR-E rotates continuously about an axis parallel to the local spacecraft vertical at 40 revolutions per minute (rpm). At an altitude of 705 km, it measures the upwelling scene brightness temperatures over an angular sector of ± 61 degrees about the sub-satellite track, resulting in a swath width of 1445 km.

During a period of 1.5 seconds the spacecraft sub-satellite point travels 10 km. Even though the instantaneous field-of-view for each channel is different, active scene measurements are recorded at equal intervals of 10 km (5 km for the 89 GHz channels) along the scan. The half cone angle at which the reflector is fixed is 47.4 degrees, which results in an Earth incidence angle of 55.0 degrees. Table 1 lists the pertinent performance characteristics.

Table 1. AMSR-E PERFORMANCE CHARACTERISTICS

CENTER FREQUENCIES (GHz) 6.925 10.65 18.7 23.8 36.5 89.0
BANDWIDTH (MHz) 350 100 200 400 1000 3000
SENSITIVITY (K) 0.3 0.6 0.6 0.6 0.6 1.1
MEAN SPATIAL RESOLUTION (km) 56 38 21 24 12 5.4
IFOV (km x km) 74 x 43 51 x 30 27 x 16 31 x 18 14 x 8 6 x 4
SAMPLING RATE (km x km) 10 x 10 10 x 10 10 x 10 10 x 10 10 x 10 5 x 5
INTEGRATION TIME (MSEC) 2.6 2.6 2.6 2.6 2.6 1.3
MAIN BEAM EFFICIENCY (%) 95.3 95.0 96.3 96.4 95.3 96.0
BEAMWIDTH (degrees) 2.2 1.4 0.8 0.9 0.4 0.18

What is LANCE?

The Land Atmosphere Near-real-time Capability for EOS provides access to near real-time data from Aqua's AIRS, AMSR-E, and MODIS instruments; Aura's OMI and MLS instruments; and Terra's MODIS instrument, within three hours of observation. Application users, operational agencies and researchers utilize these products for a wide range of purposes, from weather forecasting to monitoring natural hazards. These users often need data much sooner than available through routine science processing and are willing to trade science quality for timely access. LANCE is part of the Earth Observing System Data and Information System (EOSDIS).

Standard science products should be used for latency independent research and applications. These are available within 28-48 hours of observation from the EOSDIS Distributed Active Archive Centers. See eosdis.nasa.gov for further information about all of the NASA Earth Science data holdings.

What is the AMSR-E SIPS?

In 1997, in order to improve efficiencies within the EOS Data and Information System, NASA established the framework for the Science Investigator-led Processing Systems (SIPS). The rationale behind this framework was to enable high quality climate data products for use by Earth scientists and science application end-users, generated by personnel directly associated with the individual instrument science team and knowledgeable of the science processing algorithms, who work in close cooperation with the Distributed Active Archive Systems (DAACs). The AMSR-E SIPS is one of the first instantiations of this concept. In 2010, the AMSR-E SIPS became a part of the LANCE system and now generates near real-time products as well as the standard products.

The AMSR-E SIPS is a decentralized, geographically distributed ground-based data processing system. The two primary components are located at Remote Sensing Systems in Santa Rosa, California and at the Global Hydrology and Climate Center (GHCC) located within the National Space Science and Technology Center (NSSTC) in Huntsville, Alabama. Staffing consists of a core team of personnel, specializing in science data processing, systems administration, data management, software development, and systems engineering. Operational support is provided 8x5 and on-call.

What is the relationship between the SIPS and the GHRC DAAC?

The AMSR-E SIPS and the GHRC DAAC are co-located and they share data center staff.

What AMSR-E products are available?

NASA provides NRT and Standard Products. The standard products are provided in both a Level-2, pixel-by-pixel, orbital swath projection and in a Level-3, global space and time averaged (e.g., daily, weekly, or monthly composites) earth-oriented coordinate grid. LANCE does not generate any products with a granularity great than daily.

Table 2. AMSR-E PRODUCT AVAILABILITY

Data Set Name Standard Products Available (NSIDC) LANCE Products Available (SIPS)
AMSR-E/Aqua L2A Global Swath Spatially-Resampled Brightness Temperatures Yes Yes
AMSR-E/Aqua L2B Global Swath Ocean Products using Wentz Algorithm Yes Yes
AMSR-E/Aqua L2B Surface Soil Moisture and Q/C EASE-Grids Yes Yes
AMSR-E/Aqua L2B Swath Rain Rate/Type GSFC Profiling and Ferraro Algorithms Yes Yes
AMSR-E/Aqua L3 Global Daily Surface Soil Moisture & Q/C EASE-Grids Yes Yes
AMSR-E/Aqua L3 Daily Ascending/Descending .25x.25 deg Ocean Products Yes Yes
AMSR-E/Aqua L3 Daily 6.25 Km Polar Grids for 89 GHz TBs Yes Yes
AMSR-E/Aqua L3 Daily 12.5 Km Polar Grids for Sea Ice, Snow Depth, & TBs Yes Yes
AMSR-E/Aqua L3 Daily 25 Km Polar Grids for TBs, Sea Ice Concen & Temp Yes Yes
AMSR-E/Aqua L3 Daily Snow Water Equivalent and Snow Depth EASE-Grids Yes Yes
AMSR-E/Aqua L3 5-Day Snow Water Equivalent and Snow Depth EASE-Grids Yes No
AMSR-E/Aqua L3 Weekly Ascending/Descending .25x.25 deg Ocean Products Yes No
AMSR-E/Aqua Monthly L3 Global Ascending/Descending .25x.25 deg Ocean Grids Yes No
AMSR-E/Aqua Monthly L3 Snow Water Equivalent & Snow Depth EASE-Grids Yes No
AMSR-E/ Aqua Monthly L3 5x5 deg Rainfall Accumulations Yes No

How do I access near real-time (NRT) AMSR-E data products from the AMSR-E SIPS?

In order to access the NRT AMSR-E data products you must register for an account.

Go to http://lance.nsstc.nasa.gov/ and select the desired data set from the Products list.

You can also obtain the NRT AMSR-E data products directly from our anonymous ftp servers at:

Primary FTP location: ftp://lance1.nsstc.nasa.gov
Alternate FTP location: ftp://lance2.itsc.uah.edu

Both FTP locations are located on the UAHuntsville campus and managed by SIPS personnel, but are located in different buildings and connected to different networks. Redundant processing strings will greatly reduce the possibility of data being unavailable due to system outages.

Is User Registration required to get the LANCE data? How do I register?

Yes, you must register at https://users.eosdis.nasa.gov/urs/welcome.do before accessing data.

Can I subscribe to an RSS feed for the NRT AMSR-E data products?

Yes, you can. Click "Products" in the left menu and click an RSS feed icon next to the dataset you are interested in. You can view the feed in your browser or add it to your favorite RSS feed reader. Note that you still must register to access the files.

What is the cost of the data?

There is no charge for the data. However, you must register in order to place an order for AMSR-E data. You can register at https://users.eosdis.nasa.gov/urs/welcome.do.

How long are the data available on line? What if I want older data?

All LANCE processing centers maintain a rolling archive of 7 days. Standard products are kept for the duration of the mission; therefore, older data can be obtained from the NSIDC DAAC at http://nsidc.org/data/amsre/order_data.html.

What are the differences between the LANCE products and the standard products?

The primary difference between the near real-time L2A algorithm and the production algorithm running in the SIPS is that NRT algorithm uses static rather than dynamic calibration.

We have recently received a much improved L2A near real-time algorithm from RSS. These data are now available in our operational environments at ftp://lance1.nsstc.nasa.gov/ops/science/data/level2/l2a/ and ftp://lance2.itsc.uah.edu/ops/science/data/level2/l2a/. These L2A files are tagged R11, and correspond to the V11 standard research-quality L2A product currently available from the AMSR-E SIPS. The differences we are seeing in the LANCE NRT L2A products and the SIPS standard product L2A data files are very small.

What is the NRT data latency?

Aqua downlinks rate buffered and session based data products to the Polar Ground Stations in Alaska and Norway every 90 minutes. From the ground stations, these data travel to EDOS and then to the individual LANCE elements. The average latency from instrument observation to arrival at the LANCE AMSR-E for processing is 130 minutes. Each element then processes raw data into higher-level swath products within 20 minutes of receipt. Level-3 daily products have an average latency of 27 hours after observation of the first swath of the day.

Why should I use standard products instead of NRT products?

Standard data products are recommended for research and applications where timeliness of data is not a primary concern. These standard products are typically available within days rather than hours, and are of higher quality than the near-real-time products.

Where do I get Standard Products? What is the latency?

Standard Products are available from the National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (DAAC) at http://nsidc.org/data/amsre/order_data.html. Standard data products are available from NSIDC DAAC 4 days after the data has been collected.

What format are the data in?

Science data products are in HDF-EOS format. More information on HDF-EOS can be found at http://nsidc.org/data/hdfeos/index.html.

Is the data quality controlled?

Three major aspects of quality assurance are carried out in support of the creation of the AMSR-E standard products. These include:

  1. Automatic QA - Checking of input and intermediate data during creation of the data product
  2. Operational QA - Examination of processing diagnostics
  3. Science QA - Checking of the content of the data product during post-processing at the GHRC SIPS

Each AMSR-E Level 2A, Level 2B, and Level 3 granule has all three primary metadata flags (automatic, operational, and science) set prior to delivery to the NSIDC DAAC for archive. Upon performance of the automated checks of these aspects, the Automated QA flag, the Operational QA flag and the Science QA flag are set in the metadata (.met) file and a QA summary report is generated. If the product does not fail QA, it is then ready for use in browse generation, active science QA, higher level processing, archive, and distribution. In the event that a granule fails QA, the granule is not sent to NSIDC until it is reprocessed.

What do the various product levels represent?

Level 0 Level 0 data products are reconstructed, unprocessed instrument/payload data at full resolution; any and all communications artifacts, e.g. synchronization frames, communications headers, duplicate data removed.
Level 1A Level 1a data products are reconstructed, unprocessed instrument data at full resolution, time-referenced, and annotated with ancillary information, including radiometric and geometric calibration coefficients and georeferencing parameters, e.g., platform ephemeris, computed and appended but not applied to the Level 0 data.
Level 1B Level 1A data that have been processed to sensor units (not all instruments will have a Level 1B equivalent).
Level 2 Level 2 data products are derived geophysical variables at the same resolution and location as the Level 1 source data.
Level 3 Level 3 data products are variables mapped on uniform space-time grid scales, usually with some completeness and consistency.

Reference: http://observer.gsfc.nasa.gov/sec3/ProductLevels.html.

How are NRT products distinguished from standard products?

AMSR-E Products contain a "Product Maturity Code" within the file name to clearly indicate the products' level of maturity. Product Maturity Codes include:

B = Beta
P = Partial
T = Transitional
V = Validated
R = near Real time

The LANCE products include an "R" for near Real time in the file name for L2A, L2B and L3 data. Example: AMSR_E_L2_Rain_R10_200905281123_A.hdf.

Most Standard Products are at the validated stage and have a "V" in their file name. Example: AMSR_E_L2_Rain_V10_200905281123_A.hdf.

What are "P" files?

The AMSR-E SIPS at the GHRC DAAC has implemented incremental daily processing for our AMSR-E near real-time Level 3 daily (Ocean, Land, Snow, Sea Ice ) products. Partial products are created several times per day (currently every 3 hours) using whatever L2 data is available at the time of creation, in order to reduce latency for these products. These partial products (identified by "P") will be available in the same FTP directories as the complete real-time daily products (identified by "R"). Each new partial product for a given day will have the same file name as the previously-generated one, but will incorporate additional input files. A new partial product can be distinguished by creation time shown in the directory listing. Once the full daily file is available the partial file for that day will be deleted.

How do I cite the data?

The following example shows how to cite the use of the LANCE near real time (NRT) data sets in a publication. List the principle investigators, year of data set release, data set title and version number, dates of the data you used (for example, March to June 2004), publisher: AMSR-E SIPS, and digital media.

Ashcroft, Peter and Frank Wentz. 2010, updated daily. AMSR-E/Aqua L2A Global Swath Spatially-Resampled Brightness Temperatures V002, [list the dates of the data used]. Huntsville, Alabama: AMSR-E Science Investigator-led Processing Systems (SIPS). Digital media.

Whom do I contact for more information?

You can contact user and data services as follows:

GHRC User Services Office
National Space Science and Technology Center
320 Sparkman Drive
Huntsville, AL 35805

Phone: 256-961-7932
E-mail: ghrcdaac@itsc.uah.edu

Is documentation available?

Yes, AMSR-E dataset documentation is available from the NSIDC DAAC at http://nsidc.org/data/amsre/data_summaries.

Can the data be subsetted?

The AMSR-E SIPS plans to implement subsetting for the near real time data later in 2011. In the meantime, the GHRC DAAC does offer subsetting upon special request. Please contact the User Services Office for more information.

Are browse data available?

The LANCE AMSR-E SIPS plans to implement browse for the near real time data later in 2011.

Can I get a data subscription?

Yes, the AMSR-E SIPS at the GHRC DAAC does offer near real-time data subscriptions. With a data subscription, we will push selected data products to a designated computer as soon as the products are generated. In order to receive these products via subscription, you must be a registered LANCE user. Please let us know if you are interested in using our subscription service for AMSR-E near real-time data.

See also our RSS feeds.

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