Processing L0 ASAR Products ENVISAT


#1

Hello, i am making a tool in python for get and process the data from ASAR level 0 products of ENVISAT.

Actually, I can extract the MPH, SPH and DSDs from the files, but I have doubst with the MDS. Yes, in handbook explain a bit the structure (in 2.5.2), in Volumen 6 also explain (with less information) the MDS Structure. But is not clear (for me) what is the format of the bits? float, double, int? how can i get de raw data for decompressing and after that focalized with Range-Doppler and Omega-K algorithm?

Where can I get the “Document A-1” for a detailed description of Instrument Source Packets?

Can anyoine help me with this? give me some information or help to how to start?

And if is no much ask, also for understand better de decoding process of the data with FBAQ-4 (for image mode)

Thank you, i hope someone can help me with this =(


#2

Did you have a look at the Product Specification already ?
I think this will answer your questions. the handbook is not sufficient for implementing the reader.
https://earth.esa.int/web/sppa/mission-performance/esa-missions/envisat/envisat-product-specification


#3

Hello, thanks for answer. Yes, I saw the volumen 8 specification product but this explain in details the processed products (level 1b and level 2), but level 0 product is very superficial. I also read volumen 6 “level 0 product specification” and there, they explain better this product but I don’t understand the structure of the MDS. How can I capture this data? The header and sub header of MDS? They don’t detail if the information is char, double, float. Anyone know how to take this data? For be decoding with FBAQ algorithm later?


#4

In general there is always a description for the data, including number of bytes and data type, etc.


The Annex A contains also useful information about the format:


#5

Hello, thank you for answer again, I saw the table that you show me, but this is for an auxiliary data file. I think i dont explained well, i will try again.

I try to get the raw data of the lvl 0 products for later precess the data with focalization algorithm, but i dont understand well the MDS format of the product. Here a picture of the MDS Structure:

The “Anotations” of the MDS are well explained, also we can see the FEP anotation detailed in the same document.

In handbook, they explain a little the istrument source packet (section 2.5.2)., but they explain basically the Packet Identification" of the Packet Header. and the show this table:

For example, what is the format for the “Chirp Pulse Bandwidth”? and when start the Source packets? inmediatlly after the Resampling Factor word?

For decoding the raw data, i need to compare the block ID of this source packet with the LUTs and after how can i get the decoding value?

Thank you very much again for help me with this =)


#6

Here are also some documents, but i think more ore less the same as on the other page.
https://earth.esa.int/web/guest/-/asar-image-mode-source-packets-level-0-1437
You might contact the ESA help page https://esatellus.service-now.com/csp
They might know the right contact who can help here.
For the chirp pulse bandwidth I would guess that it is just a byte which need to be multiple by 255 and divided by 16e6