ANGELS, GSSAP, CNAV, and GPS: Guidance From Above

March 13, 2014  - By
A still from the movie Gravity, where space real estate feels really small. (credit: Warner Bros. Pictures)

A still from the movie Gravity, where space real estate feels really small and collisions frequently happen. (credit: Warner Bros. Pictures)

Wow, what a bevy of acronyms. If you already know what they mean, great. If you don’t, just hang in and all will be made clear.

E. L. Doctorow once wrote, “Writing is a socially acceptable form of schizophrenia.” Now, I am not sure how I feel about that or how my daughter who is a practicing Clinical Psychologist (PsyD) would interpret that, but as she publishes (publish or perish) behavioral science papers in the public domain, she did remind me of a paradigm shift in journalism today that has stuck with me. She said simply, “Dad, everything you publish today is out there and available to everyone, everywhere, all the time, in multiple venues.” As mundane as that may sound to everyone under 20 years of age, to those of my generation it is indeed profound, as it socially delineates the technical world we live in today that has afforded unprecedented data and document availability for the first time in history. Never before have so many had virtually instantaneous access to so much information. Can you say Siri?

The really interesting part of this instant-access phenomenon is that it not only applies to articles and columns that I and my fellow journalists pen today, but includes access to everything we, and anyone else, has ever written that has been preserved. As you read this, thousands of books (some moldering for more than two thousand years), reports and articles are being scanned daily and made available for the world to read in a digital or new print format.

Numerous major programs today are digitizing books, documents, magazines and newspapers daily, such as Amazon and the sometimes annoying Captcha program, which stands for Completely Automated Public Turing test to tell Computers and Humans Apart. In 2007 the Alfred P. Sloan Foundation awarded the Library of Congress more than $2 million for the “Digitizing American Imprints at the Library of Congress” effort. Thanks to this program and others, such as Project Gutenberg, most of the digitized volumes, 45,000 and counting for Project Gutenberg, include most of the writings of Thomas Jefferson, Benjamin Franklin and George Washington, and they are available online free of charge. Depending on your point-of-view and physical location (think Mainland China, Russia and North Korea) that can either be a scary thought or wonderfully liberating.

For almost everything written and published — and published has a new definition in this context — in the past ten years or so, and certainly for the knowable future, the digital and availability timeline equals immediate access. That is because today almost every written document originates in a digital format, while printing and publishing are secondary actions. Think about how this has changed the way you work and read today. It is truly a major revolution of epic proportions, taking place in an evolutionary manner.


Report-1Recently, I was reminded of this new electronic availability as it concerns an academic paper I was honored to edit and minimally coauthor as the Executive Officer for a very distinguished committee of preeminent scientist and physicists, more than 17 years ago when I served on a USAF (United States Air Force) Scientific Advisory Board, or SAB. I have been honored to serve on several SABs and have written or contributed to several SAB reports, but this one was particularly intriguing albeit esoteric in nature, and unless you were interested in the hazards of space debris at the time, which many of us were, you may never have heard of it until now. The full title of the report is rather lengthy, as is common with scholarly scientific reports:

“The United States Air Force Scientific Advisory Board Report on Space Surveillance, Asteroids and Comets, and Space Debris, SAB-TR-96-04, June 1997.”

A snapshot of the locations of all cataloged space objects (from the report).

A snapshot of the locations of all cataloged space objects (from the report).

The report was, at the time, and many of us feel today is still, the quintessential and defining document on the hazards or non-hazards of space debris and has been liberally quoted in scientific documents and treatises for the last 17 years.

Meanwhile, NASA (the National Aeronautics and Space Administration) as an organization has always been a bit of a harridan concerning space debris, and it has been known to sensationalize the effects that cascading space debris may have on space assets. Of course, they are always quick to point out that we academics and scientists outside of NASA only worry about absolute numbers and probabilities, while they — as the recent blockbuster movie Gravity amply exemplifies — worry about human lives in an extremely hostile space environment. This is not to say that space debris is not a valid concern; however, this SAB report clearly points out that the NASA cascading theory is more sideshow sensationalism of the Hollywood blockbuster mentality rather than supportable scientific theory. Indeed, space is a very big place, and as Einstein stated, it is always expanding — so you be the judge.

Space Surveillance

But I digress, because for the first time in recent memory, it was not the space debris aspects or Volume Four of the SAB report that made it a document of interest, but rather the First Volume on Space Surveillance that evidently piqued the USAFs interest. In Volume One, the committee made a recommendation (remember, this was seventeen years ago), that to successfully surveil space, you must do it from space and not from the Earth’s surface. Our actual recommendation in part stated, “…the committee recommends that the Air Force pursue surveillance of space from space with search capability.” And then we proceeded to move into tens of pages of technical specifics, which is more than most of you would ever want to take the time to read.

In a nutshell, as it turns out when you surveil space objects, natural and manmade from Earth, you encounter a multitude of bothersome effects you must deal with, such as weather (clouds, storms and lightening — none of which are good for sensitive optical sensors), atmosphere, solar disturbances, signal disturbances, background noise, and more. Now when you surveil space from space, most of these bothersome effects are mitigated to a major degree by the vacuum of space. In the SAB report, in much more detail than I can relate here, we basically concluded that the only successful way to continually monitor and surveil space and objects in space, both natural and man made, is to undertake that surveillance effort from space — in other words, surveil space from space — ideally from a GEO or near Geosynchronous orbit spacecraft with multiple sensors, including multi-spectral sensors that surveil both natural and manmade objects and phenomenon. Seventeen years later it appears that someone listened, and fortunately that someone belonged to an institution, the United States Air Force.

The Secret’s Out

A few weeks ago, General William Shelton, the Commander of Air Force Space Command (AFSPC) announced that by the end of the year, under a program formerly in the SECRET domain known as the Geosynchronous Space Situational Awareness Program, or GSSAP, “…the USAF plans to launch two space surveillance spacecraft into high-altitude orbits later this year to monitor satellite traffic in the congested geosynchronous belt 22,300 miles above Earth…GSSAP will produce a significant improvement in space object surveillance, not only for better collision avoidance but also for detecting threats…GSSAP will bolster our ability to discern when adversaries attempt to avoid detection and to discover capabilities they may have which might be harmful to our critical assets at these higher altitudes.” Shelton made these remarks  in a speech at the Air Warfare Symposium in Orlando, Florida, in February.

While these are not the first space surveillance satellites launched by the USAF, they are the first that peer down from on high. Currently the USAF also operates the SBSS or Space Based Surveillance Program, but these satellites surveil all of space from LEO (Low Earth Orbit) altitudes with an optical telescope. Their GEO targets are more than 22,000 miles distant. The newly announced GSSAP satellites will have much more fidelity and have the added advantage of surveilling GEO assets from GEO.


All very interesting, you say, but where does GPS come into play? Glad you asked. While the GSSAP mission will undoubtedly use limb-of-the-Earth GPS signals for guidance and orientation, the GSSAP mission will also host two other small satellites known as ANGELS, or Automated Navigation and Guidance Experiment for Local Space. The ANGELS job will be to test accelerometers and specialized algorithms that will utilize the GPS navigation signals being broadcast from 11,000 miles away in their MEO orbits, for precision guidance when in close proximity to other satellites, thereby reducing the probability of a collision. Think about this one for a while and all kinds of possibilities become apparent. Why not equip every U.S. satellite with ANGEL technology? Currently, the Air Force fact sheet on ANGELS states that the scope of the mission is limited to the space around the Delta 4 rocket’s upper stage, and while we all know from experience how dangerous inert, non-maneuverable upper stages can be, if you believe the AF fact sheet, I have some swamp land in Florida I would like to discuss.

Seriously, however the GSSAP and ANGELS missions evolve, it is still nice to know that someone is reading what you write, even if it is 17 years later.

Until next time, happy navigating and sleep well, because ANGELS really do exist.

What Is Don Reading?

Obviously I have been reading ancient but still pertinent SAB reports but more importantly this week I also read and highly recommend you read and comment on the latest Federal Register notice for comment submitted by DOT concerning deployment of GPS CNAV messages. The DOT comments are actually a bit misleading as they infer this is an early or pre-operational deployment of CNAV messages and that is a bit of a misnomer. Under the original guidelines CNAV signals would have been broadcast back in 2003 but events prevailed to prevent that from happening. However, and this is an update to the numbers in the original Federal Register Notice, there are currently 12 GPS SVs on orbit capable of broadcasting civilian L2C CNAV signals and military code or MNAV messages. Additionally there are five GPS satellites (IIFs) on orbit capable of broadcasting L5 safety of life signals for DOT.

Frankly, the DOT objects to these signals being broadcast now for, in my humble opinion, very nebulous reasons, and the USAF is working hard to and has, again in my opinion, negated all of the DOTs concerns. So please just take a couple of minutes and go to the Federal Register site and let them know how badly we need these new signals.

Hopefully, you read my February column affirming GPS as the reigning PNT Gold Standard. In order to maintain that status and indeed to continually exceed the capabilities of any of the current or planned PNT systems in existence today, the GPS needs these new signals. I predict CNAV and MNAV messaging capabilities will revolutionize the way PNT signals are utilized. These new signals bring about a capability heretofore unknown in the PNT arena. Just think about this, each CNAV and MNAV signal has the ability to broadcast 256 separate and definable messages to users globally. With 12 CNAV satellites on orbit today, global accessibility tests have shown that for the majority of users this means at least one CNAV SV in view at all times and you only need one CNAV SV in view to take advantage of the messaging capabilities. So the sooner the better I say. I don’t have the room to say much more than that this month but just imagine the possibilities. Please log onto the Federal Register site and let your opinion be heard.


This article is tagged with , and posted in Defense, Opinions

About the Author:

Don Jewell served 30 years in the United States Air Force, as an aviator and a space subject-matter expert. Don’s involvement with GPS and other critical space systems began with their inception, either as a test system evaluator or user. He served two command assignments at Schriever AFB, the home of GPS, and retired as Deputy Chief Scientist for Air Force Space Command. Don also served as a Politico Military Affairs Officer during the Reagan administration, working with 32 foreign embassies and serving as a Foreign Disclosure Officer making critical export control decisions concerning sophisticated military hardware and software. After retiring from the USAF, Don served seven years as the senior space marketer and subject-matter expert for two of the largest government contractors dealing in space software and hardware. Don currently serves on two independent GPS review teams he helped found, and on three independent assessment teams at the Institute for Defense Analyses, dealing with critical issues for the U.S. government. Don has served on numerous Air Force and Defense Scientific Advisory Boards. He writes and speaks extensively on technical issues concerning the U.S. government. Don earned his Bachelor’s degree and MBA; the Ph.D. is in progress.

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