NISAR Nodal Crossing

[peteryanics]

I have been examining NISAR soil moisture data and the timing of nodal crossings seem inaccurate. The spatial scope of my study is on El Reno, OK, co-located with an Oklahoma Mesonet site. In so doing, we are able to validate NISAR readings, and understand the picture NISAR signals are painting. It is my understanding that NISAR runs are based on 12-hour loops, at 6 AM/PM local time (or within some margin for error). However, in downloading and assessing data collection times this has been inaccurate. For NISAR-available dates in El Reno, OK (12), about 75% of them are recorded on incongruous time signatures (i.e., outside the range of error; recorded at ~8:45 PM local). While this may be a simple formulaic or writing issue, we need to understand the specificities of collection timing to sync our ground results with the NISAR inputs.

If there is any knowledge or understanding of this topic, please help us make headway, and continue with our study's focus.

[ASF - asjohnston]

Could you share the list of the 12 products you're looking at?

[peteryanics]

Sorry about that, here it is: https://search.asf.alaska.edu/#/?dataset=NISAR&prodConfig=PR&sciProducts=SME2&polygon=POLYGON((-98.0631%2035.5598,-98.0429%2035.5701,-98.0631%2035.5674,-98.0631%2035.5598))&zoom=14.784&center=-98.053,35.555&resultsLoaded=true&granule=NISAR_L3_PR_SME2_010_142_D_071_4005_DHDH_A_20260119T012543_20260119T012617_X05010_N_F_J_001

[ejfielding]

The 240 km wide NISAR swaths from adjacent tracks overlap, and they will have local acquisition times that differ by about 15 minutes.