fundamental-technologies-llc / galileo-issues-repository

Public repository for researchers and collaborators to identify and open issues related to the galileo-epd-summary data product.
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Time stamp issues #7

Closed FlynnTheMighty closed 3 years ago

FlynnTheMighty commented 3 years ago

I noticed when looking for bite out features in the particle data that the time between 64 records was around 10s and not 20s. I am including the Ganymede Ganymede.pdf moon encounters as an example. I found the same issue in all the Europa and Callisto moon encounters.

LucasMiller commented 3 years ago

Looking at galileo_epd_level2_lunar_ganymede-ver-1.1.1-01.csv Timestamp for first 64 sector record (FileSpinNumber=4, RecordType=1): 1996-250T18:33:33.451 Timestamp for last 64 sector record in that spin: 1996-250T18:33:52.156

DeltaT in this case is approximately the expected 20 second spin period. This pattern appears to continue... am I missing something?

FlynnTheMighty commented 3 years ago

I might be misunderstanding the structure of the CSV file. Here is the first 64 times stamps from the Ganymede csv file. First64TimeStampsOfCSV.pdf

I thought the first record (2) after the header and the 66th should be 20s apart.

LucasMiller commented 3 years ago

Ahhh... no, the RecordMode 64 (RecordType = 1), 32 (RecordType = 2), and 16 (RecordType = 3) sector records are all interleaved in this file.

If you want to work with the high resolution RecordMode records then sort the CSV file on the RecordType column and keep RecordType =1. After that records that are a spin apart (approx 64 records if there was a full spin of data) will have timestamps that differ by about 20 seconds.