GPS turns 30 years old, and 32 satellite constellation as of tomorrow

[TangoWhiskey]

GPS Hits the 30-Year Mark
Feb 26, 2008

February 22 marked the 30th anniversary of the first GPS signal in space with the launch of NAVSTAR 1 from Vandenberg Air Force Base.

"The Block I satellites, launched between February 22, 1978, and October 9, 1985, paved the way for an operational system that has revolutionized the way we go to war," said Col. David Madden, GPS Wing Commander at Los Angeles Air Force Base. To mark the occasion, Rockwell International made a special "first-day-of-issue" card for each Block I launch and arranged for the Vandenberg AFB post office to stamp them with the date of the launch.

The Block I contract, F4701-74-C-0527, was signed in August 1974. The first satellite launch was 42 months later, and the first four satellites launched within the space of a year * all in 1978.

Next year will see the 20th anniversary of the first officially operational Block II satellite, launched February 14, 1989. "Mission II-1 was a momentous occasion, starting the full operational constellation that the world now relies upon for precise navigation signal in space," Madden noted.


32 GPS Satellites: Today Is the Day
Feb 26, 2008

Today will be the historic day that GPS users see a healthy, 32-satellite constellation orbiting the earth, if all goes according to plan.

The U.S. military's GPS administrators issued a Notice Advisory to NAVSTAR Users (NANU) this morning advising that satellite SVN23, transmitting L-band code as PRN32, would be set to healthy as of 18:00 Zulu today, "Zulu" being the military and civil aviation term for Coordinated Universal Time. In civilian terms, that translates to 1 p.m. Eastern Standard Time in the United States.

The PRN32 designation is notable among other reasons because it is the first time that the PRN32 designation will be used by an operational, healthy GPS satellite * and the first time there have been 32 satellites designated healthy within the GPS constellation. The military had originally advised February 7 that SVN23 would be set to healthy, but then announced a delay of that designation February 20.

When it is set to healthy, some older GPS receivers might not be able to see it; GPS receivers initially were built to accommodate up to 31 satellite signals, and a PRN designated with the number 32 can't be tracked by some manufacturers' devices that look for PRNs numbered 0 through 31; typically these are older-model receivers.

The U.S. Air Force began testing the PRN32 designation late in 2006. While SVN23/PRN32 was set to unhealthy and not included in the operational GPS constellation almanac, some all-in-view GNSS tracking stations received the L-band signal. As of January 2007, SVN23 has been broadcasting steadily but set to unhealthy and not included in the almanac. Nevertheless, a number of civilian users have reported being able to track PRN32 since then.

 

[KennyFlys]

I'm curious when it first became declassified and later available for public use.

 

[Ghery]

I'm curious when it first became declassified and later available for public use.

Can't say, but I got my Garmin 45 for the boat for Christmas in 1994. It was well established for public use then.

 

[Joe B]

Trimble introduced the first civilian GPS receiver in 1984.

Regards,
Joe

 

[TangoWhiskey]

I'm curious when it first became declassified and later available for public use.

Interestingly, public access to GPS signals came about due to the Soviet shootdown of the Korean Airlines flight... in 1983 Reagan mandated that the constellation be made available to the public (albeit at a reduced accuracy) to help prevent a future occurrence of such an event.

Also of interest below is what Bush did in 2004 to keep GPS free of direct user fees.

Source: http://www.america.gov/st/washfile-english/2006/February/20060203125928lcnirellep0.5061609.html


THE EARLY DAYS OF GPS

Like the Internet, which arose from a 1969 research project of the U.S. Defense Department, GPS began as a military research project in the 1960s and 1970s. The idea was to fly atomic clocks on satellites and use the data for navigation.

The system has several components: a constellation of 24 NAVSTAR satellites (operated by the U.S. Air Force) in Earth orbit with atomic clocks aboard, ground stations that control the system, five on-orbit spare satellites and receivers for users.

GPS satellite launches started in 1978, and second-generation satellites were launched beginning in 1989. The system became fully operational in 1995, with a signal for military users and a less-accurate signal for civilians, but the commercial market had begun to open up more than a decade earlier.
In 1983, Soviet jet interceptors shot down a Korean Air civilian airliner carrying 269 passengers that had mistakenly entered Soviet airspace.

Because crew access to better navigational tools might have prevented the disaster, President Ronald Reagan issued a directive guaranteeing that GPS signals would be available at no charge to the world when the system became operational. The commercial market has grown steadily ever since.

In 2004, President Bush issued an updated policy that keeps civilian GPS free of direct user fees.

 

[KennyFlys]

Troy, Thanks for the info!