GEDI 'system response impulse' or 'return impulse response'

Use this Forum to find information on, or ask a question about, NASA Earth Science data.
Post Reply
ctampion
Posts: 14
Joined: Sat Nov 14, 2020 4:21 am America/New_York

GEDI 'system response impulse' or 'return impulse response'

by ctampion » Fri Feb 18, 2022 3:07 am America/New_York

Hello,
Is there any info available regarding the 'system response impulse' / 'return impulse response' for the GEDI instrument? For context, this would assist with deconvolution of the GEDI waveform.
Thanks in advance.

Tags:

ASDC - cheyenne.e.land
User Services
User Services
Posts: 77
Joined: Mon Mar 22, 2021 3:55 pm America/New_York
Answers: 1
Been thanked: 3 times

Re: GEDI 'system response impulse' or 'return impulse response'

by ASDC - cheyenne.e.land » Fri Feb 18, 2022 12:18 pm America/New_York

Hello,

We have contacted someone from GEDI and they have stated that:

The transmit pulse for each laser shot is the “impulse response” of GEDI for that channel/shot and is contained in the L1B data record.
The transmit pulse is the system response to the transmitted laser pulse and is the narrowest stimulus GEDI sees (Other than some radiation events, but that is another topic).

If you are looking for the response of the system to an actual “impulse” (i.e. infinitely narrow stimulus pulse), we do not have that.
We did some narrow pulse (2-3 nsec FWHM) testing prior to launch but that data was only for limited conditions.
Note that very narrow band impulses (< 1 nsec) create some overshoot/undershoot artifacts.

Hope this helps.

ctampion
Posts: 14
Joined: Sat Nov 14, 2020 4:21 am America/New_York

Re: GEDI 'system response impulse' or 'return impulse response'

by ctampion » Fri Feb 18, 2022 4:26 pm America/New_York

Hello,

Thank you for that. I assume the person from GEDI is referring to the txwaveform layer/field which is easy enough to extract.

I am no expert on this, as you probably already tell, but my understanding is that deconvolution also requires a kind of "blank response" or control sample so that artifacts from the system can be isolated from actual signal in the return waveform, e.g. see:
https://www.spiedigitallibrary.org/conf ... hort?SSO=1

and:
https://www.sciencedirect.com/science/a ... 1616304968

I'm not sure if that helps to clarify what I'm after and whether it actually exists.

Thanks again for your help on this.

ASDC - cheyenne.e.land
User Services
User Services
Posts: 77
Joined: Mon Mar 22, 2021 3:55 pm America/New_York
Answers: 1
Been thanked: 3 times

Re: GEDI 'system response impulse' or 'return impulse response'

by ASDC - cheyenne.e.land » Fri Feb 25, 2022 7:08 am America/New_York

Hello,

They would recommend you use the transmit pulse (tx waveform) as the impulse response for deconvolution. If noise is an issue, then you could average several TX waveforms together or lowpass filter them to get a cleaner version.

Thanks

ctampion
Posts: 14
Joined: Sat Nov 14, 2020 4:21 am America/New_York

Re: GEDI 'system response impulse' or 'return impulse response'

by ctampion » Thu Mar 17, 2022 9:45 pm America/New_York

Hello,

Only just spotted your 25 Feb reply. I'll give that a go.

Thanks again for your help.

Post Reply