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Jet Propulsion Laboratory California Institute of TechnologyAIRSAR Airborne Synthetic Aperture Radar
HOME NEWS DATA DOCUMENTATION
   
    Frequently Asked Questions (FAQ)

         AIRSAR Data Collection

o        AIRSAR Data Mode

         AIRSAR Data Products

o        AIRSAR Survey Data

o        AIRSAR Precison Data

         AIRSAR Data Request

o        How do I determine if precision data exist for a specific flight line?

o        How do I request copies of already processed data ? How long will it take ?

o        How do I request precision data processing of new products ? How long will it take?

o        How much overlap should be allowed between adjacent precision data products from the same flight line ?

         AIRSAR Data cost

         The peg-point in the TOPSAR data                                        

 

AIRSAR Data Collection

 

Question:  What are the various AIRSAR data modes ?

 Answer:

Although the modes can vary slightly with each flight season and the permission to collect data different bandwidths does vary with country.

The following are the standard AIRSAR modes:

         POLSAR: C-band, L-band, P-band polarimetric data.

         TOPSAR: C-band DEM data , C-band VV, P-band Polarithmetric data.The P-band data will be a slant-range POLSAR, if the P-Band is a 20 MHz data and the DEM is a 40 MHz data.

        Along-track Interferometry(ATI): C-L-band ATI

             

AIRSAR Data Products

Question:  What are AIRSAR survey data?

Answer: 

         AIRSAR survey data are low resolution (100 meter), single channel image products that show all of the imaged area from a single flight line. They are not calibrated and no motion compensation is performed during survey data processing. They are intended as browse products from which to select areas for higher resolution precision processing and are not for quantitative data analysis. These products are annotated with information about the flight line at the top and frame count and geographic information along the side of the image that refers to specific tick marks. There are 20480 frame counts between tick marks which corresponds to approximately 10 km in distance.

The latitude/longitude annotation of the survey image is the target terrain location approximately since 1999. Before the year 1998, the latitude/longitude annotation of the survey image was the airplane location in the air.

You may have trouble displaying a survey image due to the large size of some of the files and your browser limied. If this occurs, try downloading the image to your local disk and opening it with another image display program.

To determine if precision data have been processed from a flight line, or to request precision data processing click on "Browse/Order Precision Data".

 

Question:  What are AIRSAR precision data?

 Answer:

AIRSAR precision data are calibrated datasets that contain all of the data channels that were collected during a flight line. The precision data have a job id number that has a CM, TS or AT prefix where:

CM = polarimetric (POLSAR) data in the compressed stokes matrix format in the slant range projection

TS = interferometry (TOPSAR) data in I*2 format and any compressed stokes matrix polarimetric data all in the ground range projection

AT = Along track interferometry data at C-band and/or L-band

More information on these different precision products can be found in the Data Format Document under AIRSAR Data or documents on the main web page.

 
 AIRSAR Data Request

 

Question:  How do I determine if precision data exist for a specific flight line?

 Answer:

Click on "Browse/Order Precision Data" to determine if processed data exist for a flight line or to order data processing. If processed data exist for this flight line they will appear on this page with a CM, TS or AT number.

 

Question:  How do I request copies of already processed data? How long will it take?

Answer:        

        You can request duplication of existing data by selecting the products and adding them to your shopping cart. . The browse images and metadata for existing products can also be viewed. Note that the browse images should not be used for data analysis, but rather to view product coverage. In order to display the maximum amount of data at a large scale, the program used to generate these browse images may distort the aspect ratio of the data.   It typically takes 2-3 weeks to fulfill data duplication requests. The data will be written to CD-ROM and mailed to you. 

 

Question:  How do I request precision data processing of new products? How long will it take?

Answer:   

          If, after verifying that existing precision data products do not include your area of interest, you may want to request that a different segment of the flight line be processed.   

View the survey image to select the start frame count, interpolating between the tick marks on the survey image if necessary (42000 frame counts = approximately 10 km). After entering the start frame count, select the product length (in 10 km increments up to 60 km). Note that there may be a charge for new data processing.

Due to the large number of requests in the queue, processing of new precision data products can take 1-4 months. Data will be written to CD-ROM and mailed to you. The AIRSAR Science Coordinator can be contacted to determine the status of your request.

 

Question:  How much overlap should be allowed between adjacent precision data products from the same flight line?

Answer:   

          If adjacent parts of the same flight line are requested as two separate products, allow for an overlap of 10000 frame counts.

 
AIRSAR Data cost

Question:  What is the cost of AIRSAR data?

Answer:  

          Duplication of already processed AIRSAR data is done at no charge assuming that a not too large number of data products are requested.

For non-NASA funded investigators, the cost for new processing of previously unprocessed data is $750 for the first 10 km of data and $500 for 10 km segments of data requested in the same data product from the same flight line. Up to 60 km (six 10 km segments) can be included in the same data product.

Data are processed for NASA-funded investigators free of charge.

 

The peg-point in the TOPSAR data       
       

Question:  Where is the peg point located in AIRSAR TOPSAR data?

Answer:

         The peg point is located directly below (nadir) of the flight path at a point perpendicular to the center of the TOPSAR image. The peg point is not located within the image.