RE: Iridium Flares ground projection
RJ@RMATSC.RIEM.COM
Tue, 3 Feb 1998 09:42:20 -0800
The width and length of a perfect Iridium flare can be calculated as
follows:
dist = distance from the observer to the sat
alt = angle from observers horizon to the sat
1/2 = angular diameter of the sun
width = dist * tan(1/2)
length = width / sin(alt)
For an Iridium whose distance is 1200 km and 30 degrees
above the horizon the flare width would be 10 km and
length 20 km.
Real flares are far from perfect however. There is no sharp line
between light and dark and the actual flare spot would be both
larger and fuzzier.
The velocity of the flare is much harder to calculate but it would
be of the same order as the velocity of the spacecraft.
Randy
> -----Original Message-----
> From: jmonseur%mail.cpod.fr%cds.plasma.mpe-garching.mpg.de@Mail.Riem.Com [SMTP:jmonseur%mail.cpod.fr%cds.plasma.mpe-garching.mpg.de@Mail.Riem.Com]
> Sent: Tuesday, February 03, 1998 5:46 AM
> To: SeeSat-L%cds.plasma.mpe-garching.mpg.de@Mail.Riem.Com
> Subject: Iridium Flares ground projection
>
> Good morning all,
>
> To Rob.Matson, Randy John or anybody knowing:
>
> Could one see an Iridium flare projection moving on the ground
> or on the sea, e.g. from a plane or from a cliff ?
>
> What would be its width ? its speed relation with the sat ?
>
> Many thanks.
> jm
> jmonseur@mail.cpod.fr Tel. 0231 85 55 19
> GPS Lat. N. : 49d 11' 8.65" Long. W. : 0d 22' 41.2" Alt. : 48 m