Black Marble NTL data (VNP46A2)

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slbuijs
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Black Marble NTL data (VNP46A2)

by slbuijs » Mon Jul 31, 2023 12:43 pm America/New_York

I have a few questions regarding the Black Marble nighttime light data:

1. I have been unable to download anything from the LAADS Archive. Since a few days it says "Due to an outage, data is currently unavailable". Is there any information on when the data will be accessible again?

2. I understand ephemeral lights are not filtered from the A2 product (am I correct to understand that this means light sources like fires, auroras, gas flares are still present in the data?). Do you happen to know of studies that have made an effort to filter these other light sources from the daily NTL products?

3. Related to Q44 in this Q&A document: https://appliedsciences.nasa.gov/sites/default/files/Black%20Marble%20Q%26A%20Doc.pdf
Does the presence of snow (indicated by the snow flag) indicate that a snow correction has been applied for the A2? After going through the answer to Q44 this is still not entirely clear to me.

Thanks in advance!

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slbuijs
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Re: Black Marble NTL data (VNP46A2)

by slbuijs » Tue Aug 01, 2023 3:37 am America/New_York

Regarding my first question, I have found the info in the Alerts & Issues section after posting my question and will look out for updates there.

slbuijs
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Re: Black Marble NTL data (VNP46A2)

by slbuijs » Wed Aug 02, 2023 5:59 am America/New_York

While the notifications state that data downloading capabilities have now been restored at the LAADS DAAC, I am still encountering some problems.

During a batch download some files are downloading, but most files are giving one of these errors:

HTTP request sent, awaiting response... 502 Bad Gateway
2023-08-02 11:53:09 ERROR 502: Bad Gateway.

HTTP request sent, awaiting response... 504 Gateway Time-out
Retrying.

HTTP request sent, awaiting response... Read error (Operation timed out) in headers.
Retrying.

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Re: Black Marble NTL data (VNP46A2)

by LAADS_UserServices_M » Tue Aug 15, 2023 7:15 am America/New_York

1. I understand ephemeral lights are not filtered from the A2 product (am I correct to understand that this means light sources like fires, auroras, gas flares are still present in the data?). Do you happen to know of studies that have made an effort to filter these other light sources from the daily NTL products?

>>> Yes, they are in A2. In Collection 2 auroras are labeled in A1 and will be masked out in A2

2. Related to Q44 in this Q&A document: https://appliedsciences.nasa.gov/sites/default/files/Black%20Marble%20Q%26A%20Doc.pdf
Does the presence of snow (indicated by the snow flag) indicate that a snow correction has been applied for the A2? After going through the answer to Q44 this is still not entirely clear to me.

>>> While the snow flag does indicate the presence of snow, it's important to note that the Black Marble product algorithm corrects for seasonal and snow BRDF (Bidirectional Reflectance Distribution Function).
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Re: Black Marble NTL data (VNP46A2)

by slbuijs » Tue Aug 15, 2023 7:25 am America/New_York

Thanks a lot for your reply. To follow-up, I have now downloaded the VNP46A2 version of the Black Marble. So if I understand correctly, in that data cells affected by auroras have been masked out? And other light sources like fires and gas flares?

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Re: Black Marble NTL data (VNP46A2)

by LAADS_UserServices_M » Fri Aug 18, 2023 6:40 am America/New_York

VNP46A2 mask Auroras but not fires and gas flares.
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