There was good attendance at our last meeting of the year. Lots of friendly conversations as well as the mince pies!

Don’t forget, Meetings will restart on 11 Jan 2024.

Have a Happy and Safe Holiday!

Four teams of three members each too part. The questions were quite challenging, some obscure, and some looking back a good number of years.

In the end the team that won by a small margin was called “We Three Kings” (keeping in the Christmas spirit) , consisting of Paul, G1GSN, Owen, G0PHY, Ken, G4YRF.

The prize this year for the winning team members was the new Diamond Jubilee Club Mug.  Soon to be available to all club members (at a good price).

Graham started by explaining the early entries into GPS with the Navstar constellation of 32 to 38 operational satellites orbiting 20,200 km above the earth in 6 inclined planes and travelling at a speed of 14000 km per hour. He explained the launch history from 1978 to the present.

The history wouldn’t be complete without mentioning people who provided the intellect and mathematics behind the success of the system. Ivan Getting, serving as Vice President of research and engineering at the Raytheon Corp. During the 1950s they produced the concept of using an advanced system of satellites to allow precise positioning data for locating moving vehicles etc, Getting also made significant contributions to the early development of radar as well as early space flight. Ivan Getting was Born Jan 1912 and Died Oct, 2003.

Another person recognised for the development of GPS was Roger Easton, for spacecraft tracking and navigation.  Also mentioned was Bradford Parkinson for his work with the Global Positioning system allowing users to determine their location with great accuracy. Of course, this system couldn’t have succeeded without very advanced mathematics provided by Dr, Gladys West. It has been said that GPS only exists because of two people: Albert Einstein and Dr. Gladys West

Graham showed a photo of the first GPS receiver in 1977 produced by Rockwell Collins. It had a large console with two seats for operators!  In 1981 Texas Instruments produced the Navstar receiver, not very portable since it was about the size of a bread bin. Current GPS receivers are now about the size of a finger nail! So small they turn up now in watches, bracelets and phones.

Graham continued by explaining the frequencies used by GPS in use by numerous countries and an explanation of just how a position on earth can be determined by four orbiting satellites.

Of course, just putting a satellite into orbit is only the starting point because the satellite will drift slightly due to drag and gravity producing timing errors. If the on board clock is out by plus or minus one second, the position accuracy can be out as much as 300,000 km.  Graham explained how these errors are corrected to give                   accuracy within 0.3m!