Earthdata Forum

Posted: **Mon Jul 21, 2025 4:22 pm America/New_York**

Hi All,
I used to be able to access the PACE wavelengths that corresponded to wavelength_3d for the L2_AOP PACE V3 product with either this code:

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dataset_band_pars = xr.open_dataset(paths[0], group="sensor_band_parameters")
wavelength_3d = dataset_band_pars["wavelength3d"]

or ncdump:

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ncdump -v wavelength_3d PACE_OCI.20240912T171957.L2.OC_AOP.V3_0.nc

But sensor_band_parameters is no longer an accessible group (

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Errno group not found: sensor_band_parameters

), and I cannot find the wavelengths through ncdump either. Do you have any advice?

Best,
Sami

Posted: **Mon Jul 21, 2025 4:39 pm America/New_York**

Are you using an outdated version of ncdump?

./PACE_OCI.20240912T171957.L2.OC_AOP.V3_0.nc

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wavelength_3d = 346, 348, 351, 353, 356, 358, 361, 363, 366, 368, 371, 
      373, 375, 378, 380, 383, 385, 388, 390, 393, 395, 398, 400, 403, 405, 
      408, 410, 413, 415, 418, 420, 422, 425, 427, 430, 432, 435, 437, 440, 
      442, 445, 447, 450, 452, 455, 457, 460, 462, 465, 467, 470, 472, 475, 
      477, 480, 482, 485, 487, 490, 492, 495, 497, 500, 502, 505, 507, 510, 
      512, 515, 517, 520, 522, 525, 527, 530, 532, 535, 537, 540, 542, 545, 
      547, 550, 553, 555, 558, 560, 563, 565, 568, 570, 573, 575, 578, 580, 
      583, 586, 588, 613, 615, 618, 620, 623, 625, 627, 630, 632, 635, 637, 
      640, 641, 642, 643, 645, 646, 647, 648, 650, 651, 652, 653, 655, 656, 
      657, 658, 660, 661, 662, 663, 665, 666, 667, 668, 670, 671, 672, 673, 
      675, 676, 677, 678, 679, 681, 682, 683, 684, 686, 687, 688, 689, 691, 
      692, 693, 694, 696, 697, 698, 699, 701, 702, 703, 704, 706, 707, 708, 
      709, 711, 712, 713, 714, 717, 719 ;
  } // group sensor_band_parameters

Tommy

Posted: **Mon Jul 21, 2025 4:47 pm America/New_York**

Hi Tommy,
Interesting, my ncdump must be having issues...
In the wavelengths you gave in your reply, I noticed that the data is missing bands 590nm - 610nm, which have been removed in the V3 processing cited on the OB.DAAC website. However, when I open a V3 .nc file in SeaDAS (directly downloaded from the earthdata web portal), I do not see these bands missing. Instead, every band above 688nm is missing.

: Data is not removed from 590nm to 610nm; missing_wavelengths.PNG (12 KiB) Not viewed yet

: Past 688nm, there are no bands; missing_wavelengths_688.PNG (8.04 KiB) Not viewed yet

Is this an error with how SeaDAS is reading the metadata?
I am trying to get the 590nm to 610nm bands back because they are critical to a coastal ocean algorithm we are testing. We reached out to OB.DAAC and it was mentioned that these bands are still embedded in the L2_AOP product, but I cannot find them! Thanks so much for the help.

Best,
Sami

Posted: **Tue Jul 22, 2025 10:53 am America/New_York**

Yes, SeaDAS 9.2.0 has issues reading PACE V3 L2_AOP files. We'll fix it in the next release

It should look like this

: Screenshot 2025-07-22 at 10.55.36 AM.png (87.26 KiB) Not viewed yet

: Screenshot 2025-07-22 at 10.55.58 AM.png (88.41 KiB) Not viewed yet

Posted: **Tue Jul 22, 2025 11:30 am America/New_York**

Hi XuanYang,
Thank you. Is there a way to access the removed 590nm to 610nm bands in the L2 files? They are critical to a coastal ocean algorithm we are testing. We reached out to OB.DAAC and it was mentioned that these bands are still embedded in the L2_AOP product and can be accessed when downloading the files from the portal, but I was not able to figure it out. Thanks!

Best,
Sami

Posted: **Wed Jul 23, 2025 12:05 pm America/New_York**

The bands in the spectral region at the overlap between the two spectrographs in the PACE OCI instrument are not included in the v3.0 L2 products. In the v3.0 release notes, it states:

Data in the transition region between the red and blue focal planes, between 590 and 610nm, often shows significant discontinuity. Measurements in this range have much higher uncertainty and should not be used for science algorithms.

If you want to use these bands, you would need to process the data from L1 using the l2gen program distributed with SeaDAS. You would want to change the wavelength_3d input variable to not exclude the overlap region:

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current setting: wavelength_3d=346:588,613:719

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with overlap included setting: wavelength_3d=346:719

Regards,
Sean

Earthdata Forum

PACE V3 L2_AOP sensor_band_parameter group gone

PACE V3 L2_AOP sensor_band_parameter group gone

Re: PACE V3 L2_AOP sensor_band_parameter group gone

Re: PACE V3 L2_AOP sensor_band_parameter group gone

Re: PACE V3 L2_AOP sensor_band_parameter group gone

Re: PACE V3 L2_AOP sensor_band_parameter group gone

Re: PACE V3 L2_AOP sensor_band_parameter group gone