Below this introduction is part for the historic website of the GPS Signal Science Division
of the Collaborative Research Centre for Satellite Systems, the CRCSS. This Centre was directed by
Dr Elizabeth Essex-Cohen of La Trobe University, with much GPS and ionospheric research being undertaken
at La Trobe University, but other GPS related, especially more applied application research being undertaken at other Australian centres.
Readers are advised to start at the homepage of the GPS Signal Science Division of the CRCSS. The homepage includes a brief accounts of plans for CRCSS research conducted at other Australian centres. However the value of this site was greatly enhanced by providing an account of the history of satellites, and of Australia's involvement in this history.
Elizabeth Essex-Cohen with 1:1 FedSat model
The revamp of this historic webpage is dedicated to Dr Elizabeth Essex-Cohen (1940-2004)
who in 1974 was the only Australian involved in the design of
the US Air Force satellite navigation system NAVSAT, initially conceived of as a purely military system, later renamed GPS,
and made generally available when Selective Availability was turned off in May 2000.
After her initial contribution in the GPS design stage,
she returned to the US Air Force Geophysical Research Station in 1978
as a NASA Senior Post-doctoral Fellow, engaged then in basic ionospheric studies.
Returning to Australia in 1979 , she actively continued her research on the ionosphere,
and was active in lobbying for the second Australian satellite, FedSat.
She was in charge of GPS science program for FedSat.
Sadly she suddenly became seriously ill, and was hospitalised in the Xmas following the actual launch of FedSat. She had a partial remission in January 2004, enabling her to participate in an International Beacon Satellite Workshop held in Hobart, January 2004. But she then relapsed, and passed away in March 2004. After her death, a huge manual was found amongst her books, which was the Operators Manual for a Satellite of the 1960's; on her death she was probably the only Australian with over 35 years involvement with satellite technology.
To fully appreciate Elizabeth's pioneering work one needs an overview of GPS, while on this page an account is given of the GPS satellite constellation system, and brief explanation how and why the ionosphere interfere's with the use of GPS
A selection of Elizabeth's scientific papers is available here, whilst the account of her lifelong involvement in GPS is detailed here
This page updated with new images of sprites and elves replacing images from broken links dating from 1997.
Lightning, red sprites and elves with ionospheric halo
See the links and references below
>>> >>>PRESS RELEASE >>> >>>"Huge jellyfish-shaped lights in the sky above Australia's Northern >>Territory." >>> >>>A research team from the University of Otago, Dunedin, New Zealand, working >>>at "Window on the Wetlands" (60 km from Darwin) have captured 72 images of >>>"Red Sprites" on video tape on Wednesday night, 26th November. These red >>>sprites are believed to be produced by an electrical discharge from the top >>>of a thunder cloud (about 10 km altitude) to the base of the ionosphere (90 >>>km altitude). The jellyfish-shaped luminosity usually extends from 50 km >>>to 80 km and so is 30 km from bottom to top and generally about 50 km wide. >>>The dozen or so "jellyfish tentacles" hanging down are only about 1 km in >>>diameter. All of the 72 red sprites observed on 26th November are believed >>>to have occurred above the Wingate Mountains, about 250 km south of Darwin. >>> >>>Such "Red Sprites" were discovered accidentally on tape from a very >>>sensitive video camera under test in America a few years ago. Until now, >>>the only ground-based video images have been made in the USA, mainly in >>>Colorado, though some have been observed from the Space Shuttle. The Otago >>>team, lead by Professor Dowden, had previously established a link between >>>very long wavelength (15 km) radio echoes and red sprites in Colorado and >>>deduced that such radio echoes recorded in the Darwin area during the last >>>Wet season (1996/97) meant that luminous red sprites must occur above the >>>Northern Territory also. >>> >>>Although this is the first proved (video imaged) sighting of red sprites >>>from the ground outside the USA, such red sprites must have occurred above >>>NT every Wet season for millions of years. They rarely last more than a >>>tenth of a second and are generally faint, but some - certainly one and >>>maybe up to nine of the 72 caught on video on Wednesday night - can be seen >>>by the naked eye if one is well away from city lights and looking in the >>>right direction. Such red sprites must surely have been seen by the >>>Aboriginal peoples in the past, particularly before modern man polluted the >>>night sky with artificial lighting. Is there an oral tradition of such >>>sightings? >>> >>>The Otago team (Richard Dowden, John Bahr, Simon Hardman and James >>>Brundell) are indebted to the Department of Parks and Wildlife for the use >>>of Window on the Wetlands as an observatory and to Professor Zen Kawasaki >>>of Osaka University, Japan, who is currently in Darwin researching >>>lightning and lent a sensitive video camera for this purpose. >>>======================================================== >>>Caption information for photograph available on request: >>> >>>Photograph of the video screen. The jellyfish-shaped luminosity (top left) >>>extends from 50 km altitude at the bottom to 80 km (260,000 feet) at the >>>top. The side to side width is about 50 km (30 miles). The dozen or so >>>"jellyfish tentacles" hanging down are only about 1 km in diameter. The >>>numbers in white give the date and time in GMT to a hundredth of a second. >>>In NT local time this is 9:50 pm. >>>========================================================
Three of the sprites seen last Wednesday (26 Nov, 1997) are now on the web at: here
>>=============================================== >>Tempory address on campaign chasing Red and VLF Sprites: >>(until 6th December): >> >>Prof. Richard L Dowden >> >>Coolibah Resort >>91 Aralia Street >>Nightcliff >>Darwin, Northern Territory, Australia, 0810 >> >>Room Phone: +61 8 8985 4166 >>Motel Fax : +61 8 8985 4979 >>Cell Phone: +61 15 181 063 (Roaming from NZ) [leave a message] >>Email --- : email@example.com (as usual) >>