Re: ISS LIDAR System

From: Gregg Hendry <gregg.hendry_at_gmail.com>
Date: Sat, 8 Feb 2014 16:55:14 -0700
"Wouldn't the eye respond to the 'average' energy delivered per second,
which is 5000 mJ/s for CATS and only 2200 for CALIPSO?"

Good point.  At 5000 pulses/second CATS will appear as a continuous streak
whereas CALIPSO's 20.16 Hz pulse rate delivers individual spots 370 meters
apart.   Assuming the CATS "spots" are the same diameter as CALIPSO's
(about 70 meters) then an observer right on the track could be hit directly
by a portion of something like 50 pulses.

That could be quite bright  -  well worth the effort to look.

Gregg Hendry




On Sat, Feb 8, 2014 at 4:03 PM, David Tiller
<dtiller_at_captechconsulting.com>wrote:

> Wouldn't the eye respond to the 'average' energy delivered per second,
> which is 5000 mJ/s for CATS and only 2200 for CALIPSO?
>
> On Feb 8, 2014, at 17:57, "Gregg Hendry" <gregg.hendry_at_gmail.com> wrote:
>
> > According to the referenced web site:
> >
> > "While CALIPSO can deliver 20 pulses of laser per second, using, as
> > McGilldescribed it, a whopping 110
> > milliJoules of energy in each of those pulses, CATS will fire 5,000 laser
> > pulses per second, with only about 1 milliJoule for each pulse."
> >
> > With less than 1 percent of CALIPSO's laser power CATS would be quite
> > difficult to see.  One would have to be within 100 meters or less of the
> > laser's ground track to see anything but a brief green twinkle.  I am
> > guessing that under ideal conditions an observer exactly on the ground
> > track could see a short green streak maybe 1 degree wide and 5 to 10
> > degrees long.
> >
> > On the plus side though, the ISS comes around occasionally at a
> reasonably
> > civilized hour.  CALIPSO only appears in shadow around 2:30 AM
> >
> > Gregg Hendry
> >
> >
> > On Wed, Feb 5, 2014 at 5:27 AM, DAVID DICKINSON <ghedi_dave_at_yahoo.com
> >wrote:
> >
> >> Interesting; a LIDAR system similar to the one used by CALIPSO is headed
> >> to the ISS later this year;
> >>
> >>
> >>
> http://www.nasa.gov/mission_pages/station/research/news/cats_in_space/#.UvItiPldWb7
> >>
> >>
> >> I wonder if it'll be visible on shadow passes of the station?
> >>
> >> Thanks,
> >>
> >> Dave Dickinson
> >> Blog: www.astroguyz.com
> >> Twitter: http://twitter.com/Astroguyz
> >> Youtube: http://www.youtube.com/astroguyz
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Received on Sat Feb 08 2014 - 23:56:03 UTC

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