And more of them!
That’s been one of the mantras — a controversial one, granted — of technological advance in the late 20th and early 21st centuries. It has succeeded in penetrating the global positioning, navigation, and timing vanguard, as evidenced by a handful of key presentations on the first day of the Institute of Navigation (ION) International Technical Meeting in San Diego on Monday.
Skybox Imaging, a company that is “passionate about bringing Moore’s Law to space via disruptive microsatellite technology, rapid development cycles, and a scalable web-based delivery platform,” spoke to the ION ITM plenary session in the person of Ronny Votel, an engineer leading the company’s guidance, navigation and control division. Skybox’s goal is to provide “easy access to reliable and frequent high-resolution images . . . through a “constellation of imaging microsatellites delivering high-resolution imagery of any spot on Earth multiple times per day.”
To achieve that goal, Skybox is developing a low-cost imaging satellite system:
- design life of the satellites, 3 years;
- size of the satellites, a mini-fridge;
- size of the constellation, in the tens.
Skybox will pair that flying system with web-accessible big data processing platform to capture video or images of any location on Earth within a couple of days — an unheard of delivery turnaround in the current global imaging industry, unless you happen to be a government (as in central, high, federal, perhaps military) customer.
The low-cost nature of the satellite opens the possibility of deploying tens of satellites which, when integrated together, have the potential to image any spot on Earth within an hour. Votel several times made the analogy in his talk of using an iPhone camera to capture desired imagery, and indeed that could be a next logical step in FBC development: just throw a bunch of camera phones up into orbit.
Skybox expects to launch its first two satellites later this year.
In April of last year, Wired published a fascinating history and analysis: “Smaller, Quicker, Secret, Robotic: Inside America’s New Space Force.” Between Between 1992 and 1999, the U.S. National Aeronautics and Space Administration (NASA) launched 16 faster, smaller, cheaper missions, including Mars probes and space telescopes. Ten missions succeeded; six failed. Analysts declared the initiative a failure, and to a large extent it has been forsaken. Recent public writings, though, show second thinking. “I would like to respectfully suggest that success-per-dollar is a more meaningful measurement of achievement than success per-attempt,” stated one Air Force lieutenant colonel in a treatise on program management lessons from NASA.
Could such an approach work for GNSS satellites, some of which are burdened with extraneous non-PNT payloads that make them far from FSC? Time will tell the wiser.
Microtechnology
In that FSC vein, at one of the afternoon’s technical sessions, Andrei Shkel of UC-Irvine had been scheduled to deliver a paper on “Precision Navigation and Timing Enabled by Microtechnology,” but apparently something came up and he was not able to appear. I had looked forward very much to what I anticipated would be an update to his September 2011 article in GPS World, “Microtechnology Comes of Age,” which was itself an update to a plenary talk he gave at ION ITM back in 2011. For now, that article will have satisfy us.
Other presentations in the same MEMS, atomic clock, and MicroPNT session:
Michael Bulatowicz of Northrop Grumman talked about a DARPA-backed project, the nuclear magnetic resonance (NMR) gyroscope. Northrop’s development and research has shown a viable solution to producing a small (size of a U.S. quarter coin) low-power navigation grade gyro using non-vibratory technology. The company has produced two prototypes and is at work on two more. Feed the NMR gyro into Shkel’s work and who knows what you’ll get in terms of FBC PNT? Well, maybe not cheaper in the immediate future. Bulatowicz said that as an assembled device he expected its cost, at least initially, to be substantially higher than MEMS technology.
Richard Waters of Lumedyne Technologies spoke on next-generation MEMS inertial sensors with white-noise characteristics, a new paradigm based on time-domain switching for how MEMS sensors might work. TDS inertial sensors provide some key benefits: a purely digital approach, recalibration due to bias drift is not required, output is independent of oscillator conditions. Power is low, less than 1 millwatt. The device demonstrated switch stability under static conditions to –170 db. The same TDS concept can also be applied to a mechanical gyro.
QZSS
In other ION ITM first-day news, H. Tokura of the Tokyo University of Marine Science and Technology talked about “The Possibility of Precise Automobile Navigatin using GPS/QZS and Galileo E5 Pseudoranges.” Currently, research and prototype automobile high-precision PNT is done with real-time kinematic (RTK) networks, but this has some disadvantages, as discussed in an article by authors from the University of Nottingham, UK, in the February issue of GPS World.
Japan’s QZSS now broadcasts L5 signals. Japan has essentially leapfrogged the United States, since the L5 signals with full CNAV message is already broadcast by satellite QZSS-1. Currently, three U.S. GPS satellites are L5 CNAV-capable, but none are broadcasting such a signal.
Tokura showed results demonstrating that pseudorange observables from L5 are basically robust enough for this task. Further investigation for L5 is required because manufacturers are still developing the tracing technique for the new L5 signal. A software-defined receiver is indicated for usage.
Hideki Yamada of Japan’s Electronic Navigation Research Institute spoke about the possibility of using only the QZSS constellation, “in case of GPS failure,” for RTK positioning in precision ag and machine control, with 4 to 7 QZSS satellites that could be launched in a future version of the constellation. QZSS has been shown to provide 10-meter accuracy in absence of GPS; now the research looks at an RTK method.
With only one satellite in orbit, RTK-QZSS cannot be tested in the field. The researchers simulated a fuller constellation by using QZS-1, Multifunctional Transport Satellites (MTSAT), a set of geostationary weather and aviation control satellites, and GPS signals. Using a JAVAD Alpha receiver, Trimble and NovAtel antennas, they obtained results with low multipath error (about 30 centimeters) in a Tokyo environment. Multi-epoch processing is necessary for RTK-QZSS. This solution can work well as a minimum backup system of high-precision position under relatively moderate DOP condition.
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