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Jun

How to get SHARAD data ground track

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Hi all,

Greetings!

 

In the PDS node (http://geo.pds.nasa.gov/missions/mro/sharad.htm), for the Derived Data Products (DDR), the lbl files hold the information for the data file). In the lbl files, there are for values for the latitude and longitude:

 

MRO:START_SUB_SPACECRAFT_LONGITUDE = 97.749998 <DEG>

MRO:START_SUB_SPACECRAFT_LATITUDE = -24.689301 <DEG>

MRO:STOP_SUB_SPACECRAFT_LONGITUDE = 95.934470 <DEG>

MRO:STOP_SUB_SPACECRAFT_LATITUDE = -37.625862 <DEG>

 

However, if one observation has a very large latitude range (say 30 - 50 degrees), using only two points (start and end) can not show the accurate ground track (since Mars is rotating). If I only have two points and the straight line between them, it is not correct (I guess the real ground track should looks curve ?)

 

So how can I get accurate ground track for each orbit?

 

Thanks in advance,

Jun

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Jun,

The label gives you the starting and ending sub-spacecraft points for the entire SHARAD file. Each record in the file has information about a single SHARAD observation, including the sub-spacecraft latitude and longitude at the time of the observation. You'll find these in columns 77, 78, and 79 of each record. See the file RDR.FMT in the LABEL directory of the archive for a description of all the columns. Both the planetocentric and planetographic latitude values are recorded. (For an explanation of the difference, see the PDS Standards Reference, section 2.4, Body-Fixed Planetary Coordinate Systems.)

I hope this helps you.

Susan Slavney

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Hi Susan,

Thanks for the quick reply! I really appreciate that!

 

I think it will work :)

 

best regards,

Jun

Jun,

The label gives you the starting and ending sub-spacecraft points for the entire SHARAD file. Each record in the file has information about a single SHARAD observation, including the sub-spacecraft latitude and longitude at the time of the observation. You'll find these in columns 77, 78, and 79 of each record. See the file RDR.FMT in the LABEL directory of the archive for a description of all the columns. Both the planetocentric and planetographic latitude values are recorded. (For an explanation of the difference, see the PDS Standards Reference, section 2.4, Body-Fixed Planetary Coordinate Systems.)

I hope this helps you.

Susan Slavney

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I have a question regarding the SHARAD RDR products. I noticed that the rdr.fmt

file describes several geographic parameters in each data record.

 

http://pds-geosciences.wustl.edu/mro/mro-m-sharad-4-rdr-v1/mrosh_1001/label/rdr.fmt

 

Specifically, I see the SUB_SC_PLANETOCENTRIC_LATITUDE and SUB_SC_EAST_LONGITUDE.

 

I realize that this point may not coincide completely with the actual footprint of

SHARAD on the surface. That depends on how far off nadir the instrument aims.

Does SHARAD acquire data sufficiently off nadir such that I need to apply SC_YAW_ANGLE,

SC_PITCH_ANGLE and SC_ROLL_ANGLE to determine the Mars surface intercept points?

 

Are the ground intercept points perhaps described elsewhere in the rdr.fmt?

 

 

Thank you,

Jun

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