Re: OT Satellite images

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Ivan Shmakov

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Sep 6, 2018, 12:57:39 PM9/6/18
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>>>>> Jeff Liebermann <je...@cruzio.com> writes:

[Cross-posting to the mostly inactive news:sci.geo.eos, as the
subject being discussed seems perfectly on-topic there.]

[...]

> <https://terra.nasa.gov/about/terra-instruments/modis>

MODIS> With its sweeping 2,330-km-wide viewing swath, MODIS sees every
MODIS> point on our world every 1-2 days ...

> So, that's 24 to 48 hrs per image which is not exactly "real time".

> <https://en.wikipedia.org/wiki/Moderate_Resolution_Imaging_Spectroradiometer>

I haven't read the entire thread (yet), so apologies if I miss
a thing or am repeating someone, but I'd like to point that you
aren't exactly limited to using a single satellite. So, you can
use MODIS onboard both Terra and Aqua, VIIRS/Suomi NPP, and five
NOAA/POES satellites (per [1]) with AVHRR onboard of each.

Depending on the latitude, and on how their orbits (and ground
tracks) align, that may give something around 3 hours per image.

Unless I be mistaken, each of the aforementioned satellites
supports direct broadcast.

[1] https://en.wikipedia.org/wiki/Polar_Operational_Environmental_Satellites

> Resolution is (mostly) 1 km. I don't know which bands or what
> algorithms are used for fire detection:
> <https://modis.gsfc.nasa.gov/about/specifications.php> Looks like:

> Channel Central Purpose number wavelength (µm)

> 21 4.0 High-range channel for active fire detection.
> 22 4.0 Low-range channel for active fire detection.
> 31 11.0 Active fire detection, cloud masking, forest clearing rejection.

IIRC, the in-file descriptions of the MODIS data products tended
to be rather detailed as to which source data got used for what.
It may thus make sense to look there as well.

That said, I have no idea where one obtains processed MODIS data
nowadays. I suppose the links in the Wikipedia article referenced
above are largely outdated.

> Note that the raw data can be received directly from the satellites:
> <https://modis.gsfc.nasa.gov/data/directbrod/>

I happen to have a 1192 MHz to 90 MHz converter from a EOS
receiver at work. (Can't recall if it's part of the Terra or
Aqua signal pathway.) As far as I can tell, its local oscillator
is dead; and with only (guesstimated) dozens of units being ever
produced, the chances of finding a working and ready to use
replacement are rather slim.

(Which makes me wonder if perhaps someone could point me to some
kind of a reference on designing oscillators in the 1 GHz range?)

[...]

--
FSF associate member #7257 http://softwarefreedomday.org/ 15 September 2018

69883925...@nospam.org

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Sep 6, 2018, 1:13:44 PM9/6/18
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Ivan Shmakov wrote
> MODIS> With its sweeping 2,330-km-wide viewing swath, MODIS sees every
> MODIS> point on our world every 1-2 days ...
>
> > <https://modis.gsfc.nasa.gov/data/directbrod/>
>
> I happen to have a 1192 MHz to 90 MHz converter from a EOS
> receiver at work. (Can't recall if it's part of the Terra or
> Aqua signal pathway.) As far as I can tell, its local oscillator
> is dead; and with only (guesstimated) dozens of units being ever
> produced, the chances of finding a working and ready to use
> replacement are rather slim.
>
> (Which makes me wonder if perhaps someone could point me to some
> kind of a reference on designing oscillators in the 1 GHz range?)

I use Sirenza VCOs in some of my designs:
https://www.ebay.com/sch/i.html?_odkw=silenza+VCO&_osacat=0&_from=R40&_trksid=m570.l1313&_nkw=sirenza+VCO&_sacat=0
very stable VCOs in my experience and cheap on ebay.

BTW likely you can receive that sat with an RTL-SDR stick, I do receive weather sats with it.
That modis . gov link reports as untrusted here, so I do not want to look up that .goc site.

Jeff Liebermann

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Sep 6, 2018, 6:57:36 PM9/6/18
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On Thu, 06 Sep 2018 16:57:36 +0000, Ivan Shmakov <iv...@siamics.net>
wrote:

> That said, I have no idea where one obtains processed MODIS data
> nowadays. I suppose the links in the Wikipedia article referenced
> above are largely outdated.

Try NASA Direct Readout Labs;
<https://directreadout.sci.gsfc.nasa.gov/>
The interesting stuff is under Links:
<https://directreadout.sci.gsfc.nasa.gov/?id=MODIS&num=2>
and under Downloads:
<https://directreadout.sci.gsfc.nasa.gov/?id=dspContent&cid=12>

Also see:
NASA Earthdata MODIS Subsets:
<https://earthdata.nasa.gov/earth-observation-data/near-real-time/rapid-response/modis-subsets>
which will soon be replaced by Worldview
<https://worldview.earthdata.nasa.gov/>
and GIBS (Global Imagery Browse Services)
<https://earthdata.nasa.gov/about/science-system-description/eosdis-components/global-imagery-browse-services-gibs>

If you want to try receiving Terra, Aqua, and others:
<https://en.wikipedia.org/wiki/Earth_observation_satellites_transmission_frequencies>
Looks like a really old frequency list and I'm too lazy or busy to
find something better. Well, here's Terra and Aqua:
<https://earth.esa.int/web/eoportal/satellite-missions/t/terra>
8212.5 OQPSK and 8160 SQPSK MHz both using some kind of protocol by
the CCSDS:
<https://standards.nasa.gov/ccsds-standards>
<https://public.ccsds.org>
I was about to recycle all the X-band junk that I've accumulated over
the years, but maybe I'll try throwing together a tracking satellite
dish antenna and X-band receiver. (Yet another project).

> > Note that the raw data can be received directly from the satellites:
> > <https://modis.gsfc.nasa.gov/data/directbrod/>
>
> I happen to have a 1192 MHz to 90 MHz converter from a EOS
> receiver at work. (Can't recall if it's part of the Terra or
> Aqua signal pathway.)

EOS makes GPS/GNSS receivers.
<https://eos-gnss.com>
1192 Mhz is in the GPS band. The RF components might work, but you'll
probably need a higher IF frequency to handle the 30Mhz occupied
bandwidth used by Terra.

> As far as I can tell, its local oscillator
> is dead; and with only (guesstimated) dozens of units being ever
> produced, the chances of finding a working and ready to use
> replacement are rather slim.

What make and model? It might be easier to repair than to install a
new LO. However, all you'll be able to receive is NOAA 17, 18, etc on
L-band. The birds you want to chase are probably all on X-band.

> (Which makes me wonder if perhaps someone could point me to some
> kind of a reference on designing oscillators in the 1 GHz range?)

Sure. I have a 2K25 klystron oscillator that should provide days of
amusement and frustration.
<https://www.radiomuseum.org/tubes/tube_2k25.html>
<https://www.ebay.com/sch/i.html?_nkw=2k25+klystron>
It will probably drift badly and will certainly be rather noisy, but
might be worth the effort just for the bragging rights.

Do you want a synthesizer or fixed crystal oscillator?

My guess(tm) would be a synthesizer. I suggest one of the ADF4350 or
ADV4351 based synthesizer boards commonly found on eBay. For example:
<https://www.ebay.com/itm/292600029141>
<https://www.ebay.com/itm/141953759790>
<https://www.ebay.com/itm/173457641841>
or just get one in a box ready to play:
<https://www.ebay.com/itm/302758416068>


--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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