GOSAT flare season

From: Robert McNaught via Seesat-l <seesat-l_at_satobs.org>
Date: Sun, 12 Dec 2021 06:17:27 +0000
GOSAT  2009-002-A  NORAD 33492
14.67532006 rev/day
98.1 deg inclination

Once again we are into the GOSAT flare season at our latitude of 31S. 
The flare condition is met every 3 days due to the stable orientation of 
the satellite and an integral 44 orbits occurring every integral 3 days.

We observed regular flares from GOSAT over the southern summer solstice 
in 2019/20 and 2020/21. Last night we had our first clear sky 
opportunity and the flare was as expected at around mag -3 for a minute 
or so before shadow entry around 35deg up in the SSE. It is typically 
mag -4 at the solstice.

The "we" are myself at 149.1E, 31.3S and John Vetter at 149.4, 32.4S 
along with Steve Quirk in Mudgee and members of the Coonabarabran 
Astronomical Society. Last year it appeared that the region of maximum 
brightness was around 50km wide E-W. We are too limited to our local 
area to be clear about the central path and direction.

The peak brightness occurred around the summer solstice with the 
visibility limited by the entry into shadow - the flares visible ~5 
weeks either side of the solstice when the shadow entry is before the 
flare geometry is met.

One orbit later, the same geometry occurs 24.6deg longitude further 
west. The following table lists longitudes where the geometry is the 
same as we observe from latitude 31.3S in eastern Australia:

(Add 3 days to the date to get identical flare conditions)
         UT       Long. (at Lat. -31)
Dec 11 15:12     149.2E  Coonabarabran, NSW, Australia
Dec 11 16:50     124.7E  east of Kalgoorlie, Western Australia
Dec 11 18:28     100.1E  Indian Ocean
Dec 11 20:07      75.6E  Indian Ocean
Dec 11 21:45      51.0E  Indian Ocean
Dec 11 23:23      26.5E  Rep of S. Africa
Dec 12 01:01       1.9E  Atlantic Ocean
Dec 12 02:39      22.6W  Atlantic Ocean
Dec 12 04:17      47.2W  Atlantic Ocean
Dec 12 05:56      71.7W  N of Santiago Chile
Dec 12 07:34      96.3W  Pacific Ocean
Dec 12 09:12     120.8W  Pacific Ocean
Dec 12 10:50     145.3W  Pacific Ocean
Dec 12 12:28     169.9W  Pacific Ocean
Dec 12 14:07     165.6E  Tasman Sea
Dec 12 15:45     141.0E  Broken Hill, NSW, Australia
Dec 12 17:23     116.5E  Perth, Western Australia
Dec 12 19:01      91.9E  Indian Ocean
Dec 12 20:39      67.4E  Indian Ocean
Dec 12 22:17      42.8E  S of Madagascar
Dec 12 23:56      18.3E  N of Cape Town, Rep of South Africa
Dec 13 01:34       6.3W  Atlantic Ocean
Dec 13 03:12      30.8W  Atlantic Ocean
Dec 13 04:50      55.3W  N of Montevideo, Uruguay
Dec 13 06:28      79.9W  Pacific Ocean
Dec 13 08:07     104.4W  SE of Easter Island
Dec 13 09:45     129.0W  Pacific Ocean
Dec 13 11:23     153.5W  Pacific Ocean
Dec 13 13:01     178.1W  Pacific Ocean
Dec 13 14:39     157.4E  W of Lord Howe Island
Dec 13 16:17     132.8E  Eastern Nullarbor Plain, South Australia
Dec 13 17:56     108.3E  Indian Ocean
Dec 13 19:34      83.7E  Indian Ocean
Dec 13 21:12      59.2E  Indian Ocean
Dec 13 22:50      34.7E  Indian Ocean (E of Durban RSA)
Dec 14 00:28      10.1E  Atlantic Ocean
Dec 14 02:07      14.4W  Atlantic Ocean
Dec 14 03:45      39.0W  Atlantic Ocean
Dec 14 05:23      63.5W  W of Buenos Aires, Argentina
Dec 14 07:01      88.1W  Pacific Ocean
Dec 14 08:39     112.6W  SW of Easter Island
Dec 14 10:17     137.2W  Pacific Ocean
Dec 14 11:56     161.7W  Pacific Ocean
Dec 14 13:34     173.7E  N of Auckland, New Zealand
Dec 14 15:12     149.2E  Coonabarabran, NSW, Australia

Observers in the general vicinity of these locations (within a few 
hundred km) should expect to see some brightening of GOSAT, but I'll 
leave it to the satellite orbit gurus to derive the reflection condition 
for a general prediction of flare occurrence. I assume there is some 
sort of mirror condition (pun intended) for the Northern hemisphere 
during their summer solstice.

Cheers, Rob
Seesat-l mailing list
Received on Sun Dec 12 2021 - 00:19:22 UTC

This archive was generated by hypermail 2.4.0 : Sun Dec 12 2021 - 06:19:23 UTC