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Andy

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  1. SHARAD EDR data problems

    Dear Susan Slavney, I have read carefully these two pdf files (edrsis.pdf, rdrsis.pdf), but there still have some questions. (1) on board processing, it includes the pre-summing up to 32 echoes, and the AD is the 8-bit samples, but the SHARAD processor works in 32-bit precision, then the 32-bit samples echos data are conversed to 8-bit by compressed process called fixed scaling and dynamic scaling before transferring and downloading to earth ground. finally, the converted and compressed samples echo data are transferred to ground using the CFDP protocol. The EDR data are also expressed by 8-bit integer. so i have a question that whether the EDR data stored as 8-bit are the compressed data through employing the fixed scaling or dynamic scaling to convert the 32-bit to 8-bit on board processing or not? If it is so, the EDR data should be decompressed by reversing scaling. it means that the EDR data download from PDS website should not be utilized directly, because the decompressed process should be done before using the EDR data for observing the real echoes. Do i have correct understanding? In a word, whether the EDR data are compressed data or not? The answers are important for us, can you provide us the detailed description about EDR data including the compressed process mentioned in edrsis.pdf file ? and whether there should need the decompressed process of EDR data for upcoming data use or not ? Thanks you very much. We are looking forward to receiving answers from you. Best Regards, Andy
  2. SHARAD EDR data problems

    Dear Susan Slavney, I have read carefully these two pdf files (edrsis.pdf, rdrsis.pdf), but there still have some questions. (1) on board processing, it includes the pre-summing up to 32 echoes, and the AD is the 8-bit samples, but the SHARAD processor works in 32-bit precision, then the 32-bit samples echos data are conversed to 8-bit by compressed process called fixed scaling and dynamic scaling before transferring and downloading to earth ground. finally, the converted and compressed samples echo data are transferred to ground using the CFDP protocol. The EDR data are also expressed by 8-bit integer. so i have a question that whether the EDR data stored as 8-bit are the compressed data through employing the fixed scaling or dynamic scaling to convert the 32-bit to 8-bit on board processing or not? If it is so, the EDR data should be decompressed by reversing scaling. it means that the EDR data download from PDS website should not be utilized directly, because the decompressed process should be done before using the EDR data for observing the real echoes. Do i have correct understanding? In a word, whether the EDR data are compressed data or not? The answers are important for us, can you provide us the detailed description about EDR data including the compressed process mentioned in edrsis.pdf file ? and whether there should need the decompressed process of EDR data for upcoming data use or not ? Thanks you very much. We are looking forward to receiving answers from you. Best Regards, Andy
  3. Dear all, We now are applying the SHARAD EDR data, in order to test our compression coding technique. Whether we can directly apply the EDR data for achieving the compression coding process or not? Can you tell me what is the compression coding standard technique applied in the SHARAD or MARSIS mission? Thanks for your consideration, we are looking forward to receiving answers from you. Best Regards, Andy
  4. SHARAD EDR data problems

    Dear Susan Slavney, Many thanks for your appreciate, kind and helpful answers, these issues have been clearly resolved. I have some other questions that how the EDR and RDR data are generated. I give you my understanding that how the EDR and RDR data are generated. i think that firstly the 4 sequential echoes are summed to convert to single-observation A-scope data, whether there is average or not? then the echoes data are processed on board of spacecraft such as Doppler processing, the processed data become float 32-bit, then the processed float 32-bit data are converted to signed 8-bit integer data, and the signed 8-bit data are transferred and download to earth ground. Do i have correct understanding about the origin and how the EDR data which are stored in website as we see are generated? In addition, we give you my understanding that how the RDR data are generated. firstly, the data obtained on earth ground are signed 8-bit data, then the 8-bit data are processed on ground according to the requirements, then the 8-bit data are changed to float 32-bit again, finally the again processed float 32-bit data are stored as RDR data. Do i have correct understanding about the origin of RDR data and the how the RDR data are generated? Finally, if the 8-bit EDR data are generated from processed float 32-bit data on board, then i have a question that how the float 32-bit data are converted to signed 8-bit, and why not choose 16-bit for transferring to earth ground? Can you tell me the sampled bits digits of the applied analog to digital (AD) converter on board of SHARAD system? Thanks you very much. We are looking forward to receiving answers from you. Best Regards. Andy
  5. SHARAD EDR data problems

    Dear Susan Slavney, Many thanks for your appreciate, kind and helpful answers, these issues have been clearly resolved. I have some other questions that how the EDR and RDR data are generated. I give you my understanding that how the EDR and RDR data are generated. i think that firstly the 4 sequential echoes are summed to convert to single-observation A-scope data, whether there is average or not? then the echoes data are processed on board of spacecraft such as Doppler processing, the processed data become float 32-bit, then the processed float 32-bit data are converted to signed 8-bit integer data, and the signed 8-bit data are transferred and download to earth ground. Do i have correct understanding about the origin and how the EDR data which are stored in website as we see are generated? In addition, we give you my understanding that how the RDR data are generated. firstly, the data obtained on earth ground are signed 8-bit data, then the 8-bit data are processed on ground according to the requirements, then the 8-bit data are changed to float 32-bit again, finally the again processed float 32-bit data are stored as RDR data. Do i have correct understanding about the origin of RDR data and the how the RDR data are generated? Finally, if the 8-bit EDR data are generated from processed float 32-bit data on board, then i have a question that how the float 32-bit data are converted to signed 8-bit, and why not choose 16-bit for transferring to earth ground? Can you tell me the sampled bits digits of the applied analog to digital (AD) converter on board of SHARAD system? Thanks you very much. We are looking forward to receiving answers from you. Best Regards. Andy
  6. Dear all, I have a query that the SHARAD EDR echo data are saved by 8-bit signed integer or 8-bit unsigned integer? such as SHARAD 1689 orbit EDR data. for instance, when we read the EDR data of SHARAD 1689 orbit EDR data, which has two .data files named as e_0168901_002_ss19_700_a_a.dat and e_0168901_002_ss19_700_a_s.dat. We think that e_0168901_002_ss19_700_a_s.dat. file contains the expected echo data and the file e_0168901_002_ss19_700_a_a.dat only just contains the system information as auxiliary description of the echo data. Do we have the right understanding of this EDR data? Therefore we only emphasize on file e_0168901_002_ss19_700_a_s.dat to retrieve the expected echo data. When we extract the echo data from the file e_0168901_002_ss19_700_a_s.dat, we obtain the information that the SHARAD 1689 have 3786 bytes of each single-observations as A-scope and 4556 observations in along-track. The each observation has 3786 bytes which has last 3600 bytes contained the expected echo data, and the 3600 bytes echo data are stored as 8-bit signed integer while the header of each A--scope single observations are stored as 8-bit unsigned integer. The 186 bytes before the expected echo EDR data which has length of 3600 bytes illustrates the header system informations of each A-scope single observation data. Do we have the right understandings of the way of the data stored in .dat file? In the edrsis.pdf file, we find that there should include file E_0123405_001_SS07_700_A.data, but we can not find this file in the data storage website http://ode.rsl.wustl.edu/mars/indexDatasets.aspx. In the edrsis.pdf file, it describes that the e_0168901_002_ss19_700_a_s.dat. file is the Instrument data binary file and the e_0168901_002_ss19_700_a_a.dat represents Geometric information binary file, which can be found in page 15 in edrsis.pdf file. Can you explain these descriptions in edrsis.pdf file? Thanks you very much. We are looking forward to receiving answers from you. Best Regards, Andy
  7. Dear all, The RDR radargram data of such as SHARAD orbit 25019 (http://ode.rsl.wustl.edu/mars/indexproductpage.aspx?product_idgeo=19642615) has been obtained, but we don't know how to compensate the reative offset of ech echo. The common reference time for all echoes is described by keyword MRO:RADARGRAM_RETURN_INTERVAL = 316344 in label file (http://ode.rsl.wustl.edu/mars/indexproductpage.aspx?product_idgeo=19642615) , the shift of the first sample of a given echo from this reference time is reported as RANGE_SHIFT in rdr.fmt file (ftp://pds-geosciences.wustl.edu/mro/mro-m-sharad-4-rdr-v1/MROSH_1002/label/rdr.fmt). How to understand these two parameters and how to use them? The questions are as follows: 1. What is meaning of MRO:RADARGRAM_RETURN_INTERVAL= 316344, and what is format of 316344? integer? real?... 2. What is the meaning of the relative shift of the echo with respect to the value of the MRO:RADARGRAM_RETURN_INTERVAL in rdr.fmt? For example, the reative shift of first echo is described as two bytes 171, 253 by unit8, which is read by unit16 as 64939. then what is the relationship of the 316344 and 64939? what is the format of these two parameters or different? whether the way that we read these paramters is wrong or not ? If wrong, we should how to read then and use them? 3 what is the relationship of these time offset with 667 sampes with 0.075 microseconds sampling interval ? how to use them to compensate the offset and reestablish the true radargram? Thank you vey much. Best Regards, Andy
  8. SHARAD .dat file read

    Dear Susie Slavney, Thanks for your answer and help. The SHARAD orbit 6830 (R_0683001_001_SS19_700_A) which can be found in http://ode.rsl.wustl.edu/mars/indexproductpage.aspx?product_idgeo=12028402 is overflown the LDAs in middle latitude of Mars, whether this orbit radar data has been processed including surface clutter suppression and give the final 2-D radargram image without surface off nadir clutters or not? What are the main differences between the Reduced Data Record (RDR) and Experimental Data Record (EDR) or raw data? As i know that the surface cross-track clutters are removed on board by dipole/monopole antennas, therefore the raw data should not contian the surface cross-track clutters. That is to say that the only efficent radar data processing techniques will include SAR techiniques to remove the along track surface off-nadir clutters, which processing is applied on ground. whether my understandig is right or not? Return to my question that whether the given radargram image describe the processed radar data derived by raw data which is proceed including just Doppler filtering, dipole/monopole antenna, dual-frequency techniques or not? Best Regards, Andy
  9. SHARAD .dat file read

    Dear all, I have a queation that how to read the SHARAD data file with extension .dat such as r_2501901_001_ss19_700_a.dat with r_2501901_001_ss19_700_a.lbl for description, in order to view the 2-D radargrams. The content of this .dat file may be consisted of characters (header of file) and ASCII (radar observations with rows and colums ). This file is download from this link http://ode.rsl.wustl.edu/mars/indexproductpage.aspx?product_idgeo=19642615 Whether the given JPEG radargrams is for showing the radar data which have been compressed and surface-clutter suppression or not? In addition, i can't find the MARSIS orbit 2682 data, maybe the PDS and ESA all didn't provide these data for users or i didn't find the right place to get data. Thank you very much! Best Regards, Andy
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