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### How to convert airborne radiance to reflectance?

Posted: Mon Jun 28, 2021 5:54 am America/New_York
Dear EARTHDATA Forum,

I would like to ask one question that how to convert the airborne measured radiance data to the reflectance data?

It is known that the satellite measured radiance data can be converted to the reflectance data following this equation:
ρTOA = πLTOA/(cosθsF0)
Is this formular applicable to airborne sensors?

Thank you.
Mengmeng.

### Re: How to convert airborne radiance to reflectance?

Posted: Tue Jun 29, 2021 1:58 pm America/New_York
Hello,

If you are asking about a specific airborne sensor, the scientists who work with this sensor are likely to have written an Algorithm Theoretical Basis Document (ATBD) for it. In this document, they will spell out clearly how reflectance is defined and the nature of downward transmission and upward transmission included in their definition of the reflectance. When it comes to radiation, many people define things all sorts of different ways, so you want to see the documentation that clearly lays out all definitions for the variables with which you are working. Hope this helps.

Warm Regards,

NASA Langley ASDC User Services

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Earthdata Forum (Science Inquiries): https://forum.earthdata.nasa.gov

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### Re: How to convert airborne radiance to reflectance?

Posted: Wed Jun 30, 2021 1:45 am America/New_York
Dear NASA Langley ASDC User Services,

Thank you very much for your advice. Specifically, I want to convert radiance to remote sensing reflectance for CASI-1500 sensor.

From the ITRES Standard Processing Manual, I only found the info. that an optical sensor (Incident Light Sensor) used with CASI measures the downwelling irradiance at the roof of the aircraft during data acquisition, and the ILS allows for the correction of downwelling irradiance variatios in order to convert the CASI radiance data to the units of spectral reflectance.
But I do not have the downwelling irradiance data and I did not find the formula for the conversion.

If you have that document, could you send it to me?

Thank you.
Mengmeng.

### Re: How to convert airborne radiance to reflectance?

Posted: Wed Jun 30, 2021 8:35 am America/New_York
Hello,

Can you please provide the name of the project/collection you are getting your data from. Thank you.

Warm Regards,

NASA Langley ASDC User Services

*****************************
Earthdata Forum (Science Inquiries): https://forum.earthdata.nasa.gov

User Services (General Inquiries): support-asdc@earthdata.nasa.gov

ASDC Website: https://asdc.larc.nasa.gov

### Re: How to convert airborne radiance to reflectance?

Posted: Wed Jun 30, 2021 8:16 pm America/New_York
Dear NASA Langley ASDC User Services,

I do not know the project/collection of my data, but I only know the data was collected on April 23, 2019 from CASI-1500. My data is the calibrated radiance data in BIP format.

Thank you.
Kind regards,
Mengmeng.

### Re: How to convert airborne radiance to reflectance?

Posted: Fri Jul 02, 2021 8:33 am America/New_York
Hello,

I found one method to convert the airborne at-sensor radiance to at-sensor reflectance (Hanuš et al., 2016). In this method, the at-sensor reflectance (also called apparent reflectance) was calculated by dividing the at-sensor radiance by the downwelling irradiance.

Kind regards,
Mengmeng.

### Re: How to convert airborne radiance to reflectance?

Posted: Fri Jul 02, 2021 10:20 am America/New_York
Hello,

Do you need any further assistance?

Warm Regards,

NASA Langley ASDC User Services

*****************************
Earthdata Forum (Science Inquiries): https://forum.earthdata.nasa.gov

User Services (General Inquiries): support-asdc@earthdata.nasa.gov

ASDC Website: https://asdc.larc.nasa.gov

### Re: How to convert airborne radiance to reflectance?

Posted: Fri Jul 02, 2021 10:38 pm America/New_York
Hello,

No, I do not need further assistance for now. Thank you for your kind support.

Kind regards,
Mengmeng.