GPS World

Category: Defense

  • Leadership Talks: Is Galileo Real, or Not?

    Leadership Talks: Is Galileo Real, or Not?

    Javad Ashjaee, front left, with colleagues in his Moscow office.
    Javad Ashjaee, front left, with colleagues in his Moscow office.

    Javad Ashjaee (JA) is president and CEO, Javad Navigation Systems. Alan Cameron (AC) interviewed him by phone at his Moscow office.

    AC: What details can you give us about the “new beginning” you mentioned in your May profile?

    JA: Things have changed a lot during the past six years. ASICs, microprocessors, and electronic technology in general have progressed significantly. These advances give us much better fundamental tools to implement new signal processing innovations and to design better and smaller products, while at the same time reducing their cost. With new GPS signals, improved GLONASS, and Galileo on the horizon, there are lots of opportunities and challenges to get me going for many years again. I phrased it as a “new beginning” because in the past six years I was not as productive as I wanted to be, due to situations beyond my control.

    AC: How do you see your “complete independence” playing out in the marketplace?

    JA: Now I can start working on GNSS technology again and hope to make a difference in this field again. The last six years were the darkest years of my professional life. The partnership that I had hoped would be a complementary force in pursuing the most innovative technologies turned out mostly frustrating, and it put stumbling blocks in the way of what I wanted to accomplish. By “complete independence” I mean the contractual limitations have expired, and I am free to pursue new technologies on my own and bring innovations to the marketplace that my team and I feel proud of.

    We have just started this new round of technical development and we are trying to define the technical directions. I hope to bring a completely new generation of GNSS products to the market in the second half of 2007. What keeps me motivated and as excited as my first attempts of 25 years ago is the level of support and encouragement that I receive from all my colleagues, friends, and even some of my competitors.

    AC: What technology challenges are you and your team tackling?

    JA: One of my technology challenges is to bring high-end Galileo into the GPS/GLONASS picture. My first decade of GNSS involved GPS, the second decade GPS+GLONASS, and in the third decade I hope for GPS+GLONASS+Galileo. Of course there are also innovations in signal processing in every one of these navigation systems. As I said earlier, enhancements in the electronic industry, as always, keep pushing us to come up with new products, similar to what you see in the computer and mobile communications industries. The life of any product cannot be longer than two years.

    I’m waiting for the Europeans to tell us what is really their plan for Galileo. I want to focus a lot on Galileo but I should admit that with Galileo I’m partially hopeful, but partially disappointed, too.

    AC: Why are you disappointed about Galileo?

    JA: I basically do not know, or I should say do not understand, the current plan of Galileo as presented; and I could not find anyone who could give reasonable answers to my questions. It is not obvious who the forces behind the Galileo project are, who is going to fund it, and who needs it to the extent that they are willing to pay for it. On several occasions, in different forums I tried to raise such questions and subsequently became convinced that unfortunately my worries and questions regarding Galileo were valid. Let me raise these questions once again here with you. I hope all my worries and suspicions regarding Galileo prove to be false and sincerely hope that Galileo to become a reality soon.

    Despite all the questions and uncertainties about Galileo, but due to good publicity, in many communities Galileo has received much more attention than GLONASS, which already has about 20–25 years of on-orbit history and currently about 16 operational satellites on orbit — and recently, with current oil prices, a solid plan to complete the system soon. Until recently many companies were trying to fight or ignore GLONASS, believing that it was not likely that Russia would complete the system. Now Trimble, NovAtel, and Leica have recently announced that they have GLONASS in their receivers, too.

    The attention given to Galileo, even before they have a first real satellite, is because of the credibility that the Europeans have earned. I hope this credibility continues to grow by providing open information to the public. Unfortunately, in my belief, so far they have not done so.

    One of the issues confronting Galileo is the explanation of its funding and management. It has been said that Galileo will be funded as a private business, but no one has ever provided a business model. When I try to guess about the structure of any business plan based on the information I have received, I conclude that it is very unlikely that it can be funded as such. The fate of Iridium — which did have a detailed business plan but overestimated its number of subscriptions — makes us more worried about Galileo, which does not even have a business plan. Iridium had the support of large, experienced industrial names like Motorola.

    Any company whose stock is being traded publicly will suffer a lot as soon as they announce involvement in any project that does not have a solid business plan. The larger the company, the more vulnerable they are to close scrutiny by stock-market analysts.

    Funding in Doubt

    In providing details on Galileo funding, it was said that most of the Galileo funding will come from bank loans. This makes the issue of a business plan much more urgent and critical for Galileo, especially given the fate of Iridium. Alternatively, the money could come from specific governments. This would easily put an end to the discussion of private funding and give much hope to all of us. I hope this will happen soon.

    There are several other flaws in Galileo’s private financial planning. First, GPS tried to make itself a self-funded program but quickly concluded that it was not feasible. Second, if GPS authorities were wrong, and it could have been done as a self-funded project, now with GPS being offered for free, Galileo has a much tougher time to make it as a private enterprise. Note that GLONASS is also there for free. Can you start a pizza business, when you know the guy next door is giving away pizza for free?

    Third, it is extremely unlikely that anyone will buy Galileo-only receivers, which means Galileo wants to piggy-back itself on GPS and receive money from the operational GPS. In our pizza example, imagine that your pizza shop can sell its pizza only if it can add slices of pizza from the free shop next door! Clearly the shop next door will stop providing you free pizza if it sees you are making money — or it will at least want its share of the profit.

    The progress in GLONASS, also offered free of charge, makes it even harder for Galileo’s private plan to succeed. With 30 GPS and 24 GLONASS satellites, at any given instance we have more than 14 visible satellites. The critical number to have reliable and robust RTK is something like 10 satellites. The additional Galileo satellites are a plus, but the European system cannot survive if it bases its financial plan on riding on the shoulders of GPS (or GPS+GLONASS).

    It short, the Galileo private funding scheme assumes free support from GPS — which means Galileo assumes that U.S. tax payers will continue to fund Galileo.

    I am certain that even if GPS authorities do not object, the U.S. taxpayers will. U.S. citizens and organizations like the U.S. GPS Industry Council will take the issue to the proper authorities.

    By collecting the first license fee from users or manufacturers, Galileo authorities open the door for large international disputes that put the fate of Galileo in question and raise the issue of customer liability, if it is going to be modeled financially as I mentioned earlier.

    In the private business model of sharing profit with GPS, Galileo will be at a disadvantage for many years until they have operational satellites comparable to GPS.

    The current situation of Galileo, as I see it, is that some independent and mostly research-oriented organizations have been able to collect enough money to define signals. We have seen some published information, such as Günter Hein’s article in GPS World (“Galileo Signal and Frequency Design,” June 2003) on the signal structure. But now when the ICD is published, the signal structure is drastically different.

    The Military Question

    Similar to GPS and GLONASS, the need for Galileo mostly comes from military establishments and markets. The two recent wars showed that the benefits of satellite navigation systems are no longer a luxury, but a necessity for any country that possesses a certain level of modernized military. The French government needs its own navigation system to independently market its Exocet missiles and Mirage 2000, for example. The Chinese government also has need for such systems, and this could be the reason that they push to fund and participate in the Galileo project.

    Does this mean France will break from NATO and join forces with China? This brings us to the very difficult question of international alliances, much more serious than the financial and funding issues that I raised earlier. I find it unlikely that the United Kingdom may want an independent navigation system separate from the United States. France may be the only major country that is willing and can afford to fund such system. This is an extremely difficult issue. I cannot think of any country in Western Europe that is pushing for the breakup of NATO.

    This is an order of magnitude more difficulty than money. This is an issue of East-West alignment, and the breakup of NATO, which has many more consequences.

    It is very simple-minded if we think Paris taxi drivers are pushing to have their own system because they do not trust the United States!

    Although the European military should be most concerned about the future of Galileo, they have been absent from all the Galileo conferences that I have attended. The only European military uniforms I have seen were those of a German Air Force brass band that played Mozart songs at the Munich ENC-GNSS conference.

    At best, it seems that some large European companies have teamed up to lead the Galileo project and keep space, control, and user segments under their management and control, and then try to attract money from military sources. This scenario also does not seem to have much chance of success. It is unlikely that military organizations will allow leadership and control of their vital navigation systems to remain in private-sector hands. Under any circumstances, the military organizations will be the real force behind the Galileo even though they may hide it publicly, at least for a while.

    Galileo’s best chance of success is for the French government to pay all or at least most of the costs, and not depend on support from other countries who do not have much vital interest and dependence on a new navigation system. I hope this will happen sooner rather than later.

    Galileo is not going to delay because of technical issues. There is no problem for the Europeans to have a good signal structure, or to launch good satellites. There is enough intelligence in Europe, they can solve those quickly. Financial and, more important, political issues will determine the future of Galileo.

    Will Galileo happen or not? I have no answer. I had a chance to share my thoughts with several prominent authorities. They mostly agreed with my concerns but they said it was politically incorrect for them to even discuss these sensitive issues.

    To go forward, I will work on Galileo and will assume that the Galileo authorities will work with the GPS authorities and will make a playing field such that U.S. GPS manufacturers can have the same benefits from Galileo that Europeans have from GPS. Previously we followed the information that was released unofficially by Galileo (by semi-official authorities) and we made chips to track those signals. Next we will follow the new ICD and we will make receivers based on it.

    Meanwhile we will try to tap whatever legal authorities, the GPS authorities in the U.S., to help us make the playing field level, to make the Europeans give us the same prompt access to information that they give to European organizations, without any charge.

    The United States has been so generous and so open in providing complete and honest GPS information to all, that the first GPS satellite was actually tracked in the UK. Dr. Brad Parkinson noted this point in his keynote speech at the European Navigation Conference in Manchester.

    I was so hopeful and supportive of Galileo in the article I wrote for you some months ago. But as I tried to find information regarding the future of Galileo, I developed serious concerns. I pray for Galileo to become a reality soon.

    AC: What percentage of Javad Navigation Systems’ annual budget is devoted to research and development?

    JA: We do not have a fixed percentage. Developing technology is our first priority and has always been a priority for me. We spend whatever it takes to have the best technology, even if we have to borrow money — though we have never had to. Probably this has been the reason that in all my history of involvement with GPS, the past 25 years, we were profitable every single quarter, because our focus was spending on technology, and giving priority to it. I don’t think there is any other GPS company in the world that can claim profitability for every quarter for 25 years. Our cumulative annual growth in each company was 45 percent. Currently we have a staff of over 100. Our Advanced Theoretical Design team alone consists of more than twelve professors and scientists with more than 200 person-years of experience.

    AC: How can we best navigate the next years of new signals, structures, and so on?

    JA: The main thing is that we request all U.S. GPS authorities to help to make this a level playing field.

    If the Galileo authorities really intend to combine GPS with Galileo for commercial markets, they’d better be as gracious and open as GPS authorities were to them.

    Iridium

    Iridium communications service was launched on November 1, 1998, and went into Chapter 11 bankruptcy on August 13, 1999.

    The system was originally to have 77 active satellites (later reduced to 66) to enable worldwide voice and data communications using handheld devices. Its financial failure was largely due to insufficient demand for the service. The system is currently being used extensively by the U.S. Department of Defense for its communication purposes.

  • The Hunt for RFI: Unjamming a Coast Harbor

    The Hunt for RFI: Unjamming a Coast Harbor

    By James R. Clynch, Andrrew A. Parker, Richard W. Adler, and Wilbur R. Vincent, Naval Postgraduate School; Paul McGill and George Badger, Monterey Bay Aquarium Research Institute

    “Mr. Holmes, they were the footprints of a giant hound!”

    Engineers-turned-sleuths in Moss Landing Harbor, California, had a similar clue to go on: the tracks of a GPS jammer across a spectrum analyzer. For months, the elusive culprit had jammed GPS signals in the harbor. The team of engineers roamed the waterfront with a spectrum analyzer and receiver. They identified and apprehended not one, but two distinct suspects, and unearthed evidence of the existence of a third — all readily available, commercial-grade television antennas.

    After interrogation in the laboratory, tahe guilty devices were turned over to the authorities for appropriate action.

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    A view from the location of an unintentional GPS jammer across Moss Landing Harbor to the Monterey Bay Aquarium Research Institute. A GPS receiver with its antenna on the other side of the roof was continuously jammed for months.

    In April 2001, the captain of the research vessel PT SUR, based in Moss Landing, California, made a radio telephone call from at-sea to one of the authors, stating that signal reception of GPS in the whole of Moss Landing Harbor was jammed. He was advised to contact the U.S. Coast Guard (USCG) and the Federal Communication Commission (FCC). When the problem persisted for another month, we launched an effort at the local level to determine the cause of the jamming.

    Moss Landing is a moderate-sized harbor about 100 kilometers south of San Francisco, in the middle of Monterey Bay. It has a mixed fleet of working fishing boats, pleasure craft, and three large research vessels used by the local scientific community.

    The Naval Postgraduate School (NPS), with a large program in science and engineering, is located at the south end of Monterey Bay. The Monterey Bay Aquarium Research Institute (MBARI) has its headquarters in Moss Landing and two major research vessels berthed there. This organization supports the Monterey Bay Aquarium and also has a large engineering program, especially in underwater remotely operated vehicles.

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    Locations of the RFI emitter and MBARI; power plant upper right.

    MBARI has used GPS for precision location of their vessels since the early 1990’s, before the U.S. Coast Guard set up their system of DGPS stations along the coast. MBARI, with assistance from NPS, set up a differential station at their location at Moss Landing, using a UHF data link to send the corrections to their vessels.

    After the April jamming report, NPS set up a monitor of the MBARI DGPS corrections to log the number of satellites being tracked. This clearly showed that the station was being heavily jammed. Reports of other GPS users in Moss Landing confirmed that it was a jamming issue and not a faulty receiver.

    The jamming had impacted MBARI in several ways, including causing it to loose its GPS-based high-accuracy time reference. It would have caused difficulty at the narrow harbor entrance in fog. In at least two cases it caused small-boat owners to buy new GPS receivers, only to find they still could not get GPS in and around Moss Landing. One of the major ships in the harbor paid for a technician and new equipment to fix the problem, but finally had to turn off GPS in the harbor area, give the alarm that GPS was off line, and use radar only for harbor entrances in bad weather.

    The GPS signal that feeds the MBARI reference station was also distributed to several laboratories and offices in the MBARI headquarters building, through a series of splitters and inline amplifiers. In an office with one of these drops, we set up a high-quality spectrum analyzer to examine the energy in a wide band about the GPS L1 frequency. Because there were several long cables and amplifiers between the antenna and the spectrum analyzer, the signals were not calibrated at the time they were taken. Later the system was calibrated. Figure 1 shows an example of the data recorded with a clear peak from the radio frequency interference (RFI) source many dB above the level of the GPS signals.

    Figure 1. spectrum of Source-1 on a spectrum analyzer, VBW 3 KHz, RBW 3 KHz.
    Figure 1. spectrum of Source-1 on a spectrum analyzer, VBW 3 KHz, RBW 3 KHz.

    Identifying Source-1

    We began our search for the source of the jamming radiation in early May, 2001, spending several days looking for it. Two factors complicated the effort: the large number of metal objects that reflected the energy, and the shifting of the frequency of the emitter.

    George Badger fabricated a 17-element antenna with about a 30-degree beamwidth and used this with a portable communications receiver, a general purpose radio that fit in a shirt pocket. The initial search drove along the roads in the area and stopped at widely spaced locations to record the peaks of the RFI signal. We found multiple peaks in all locations, coming from the many reflecting structures in the area, including the largest conventional power plant in California.

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    From its normal location inside the paint locker (see arrow), the antenna jammed all of Moss Landing Harbor and an area at least 1 kilometer out to sea.

    Figure 2 shows the locations where bearings were taken as green circles, and the bearings in blue. The red circle shows the actual location of the emitter. Without the red dot, it is hard to define where the most likely position is. After ruling out the power plant, we decided to look where there were no building or other reflectors.

    Figure 2. Search for bearing for Source-1.
    Figure 2. Search for bearing for Source-1.

    Closing In. The team put the spectrum analyzer on a cart along with the small radio, and took them to the dock area. Even then it was confusing. Only by turning off shore power to individual boats could we determine the actual emitter location. The signal stopped and started again as we turned power to the vessel emitting the RFI signal off and on. The photograph, taken by a “kite camera” at about 200 meters, shows the locations of the RFI emitter, MBARI, and the power plant.

    Source-1 with cover open, showing the small preamplifier that jammed GPS.
    Source-1 with cover open, showing the small preamplifier that jammed GPS.

    We contacted the boat owner and gained access, quickly determining that the emitter was a commercially available VHF/UHF television antenna with built-in preamplifier. The antenna was powered by an AC/DC adapter plugged into boat AC power. The preamplifier was thus powered all the time, even when the TV was not on. In fact, the TV was seldom on, and most of the time the TV antenna was in a paint locker inside the locked boat. From this interior location, its emissions jammed all of Moss Landing Harbor and an area at least 1 kilometer out to sea.

    The day after we located the jamming antenna, we purchased it from the owner, took it to NPS for study, and informed the Federal Communications (FCC) San Francisco field office. We also distributed a memorandum describing the facts of the case to the U.S. Coast Guard and the GPS Joint Program Office (JPO).

    Characteristics of Source-1

    At the Naval Postgraduate School, we studied the antenna under controlled conditions and found it to have an internal preamplifier that exhibited unintended oscillations. The unit was normally powered from an inexpensive 12-volt AC/DC converter. In the tests it was powered from both this unit and a battery.

    We studied the characteristics of the emission using another spectrum analyzer with its output sent to a waterfall display.

    The unit proved extremely sensitive to the physical and electrical environment. We knew this from our search procedure, when modulation on the signal was recognized by its distinctive sound as a boat bilge pump. In an ad hoc experiment, we noted that the frequency varied over 3 MHz when one of us slowly moved his hand about 20 centimeters when it was 3 meters from the antenna. This is shown on the left in Figure 3. When the hand was held still, the frequency was much more stable, as seen by the section at the top of the traces.

    Figure 3. Frequency changes in Source-1 caused by environmental factors.
    Figure 3. Frequency changes in Source-1 caused by environmental factors.

    In another case, when running on batteries, the spectral pattern changed considerably when the overhead fluorescent lights were turned on and off. This effect is shown on the right. In order to get the narrow lines in the “lights on” condition, the spectrum analyzer was synchronized to the AC line frequency. We also found that the operation of a low-powered, hand-held transceiver (100 mW) operation at 150 MHz and 450 MHz caused large shifts in the oscillation center frequency.

    To better investigate the electromagnetic coupling, we placed the unit in a good screen room. We were interested to see if you needed an external RF field from the lights, for example. It still oscillated, indicating that the oscillation would emit RFI energy just by being turned on. No special external conditions were required.

    We obtained several other tests results, but conclude principally that the oscillation was self-exciting and very sensitive to environmental conditions.

    The Suspects Multiply

    During the hunt for RFI Source-1, NPS monitored the DGPS corrections broadcast by MBARI, automatically recording and plotting the total number of satellites for which corrections were generated every few days. While Source-1 was active, there were no satellites being tracked.

    A few days after Source-1 was removed, we again plotted this log. Much to our surprise, there were still long periods when the MBARI GPS receiver was tracking few or no satellites. The MBARI GPS receiver was being jammed during most nights. Figure 4 shows a plot of the number of satellites tracked.

    Jamming of MBARI GPS after Source-1 was removed from harbor.
    Jamming of MBARI GPS after Source-1 was removed from harbor.

    We conjectured that the jamming’s diurnal pattern derived from the temperature sensitivity of the second jammer’s center frequency. This turned out to be correct. The jamming was correlated with temperature and ended most days before 11 am.

    This told us that we would have to hunt the source location at night and early morning.

    Field Operations. The San Francisco FCC field office sent a team several times to Moss Landing to hunt for Source-2, and on several days both MBARI and NPS assisted. The MBARI high-quality spectrum analyzer monitored the signal from the laboratory this time, showing that its frequency moved during the morning hours and its level decreased as the temperature rose. We sent this frequency via cell telephone to the mobile team in the harbor seeking the RFI source. Figure 5 shows a typical early morning spectrum taken after removal of Source-1. Again the hunt was not easy.

    Figure 5 shows a typical early morning spectrum taken after removal of Source-1. Several signals are visible in this spectrum, in addition to a broad peak in the middle from the GPS satellites. This was not seen in the spectra taken earlier because Source-1 masked it. The peak in the GPS band comes from Source-2.
    Figure 5 shows a typical early morning spectrum taken after removal of Source-1. Several signals are visible in this spectrum, in addition to a broad peak in the middle from the GPS satellites. This was not seen in the spectra taken earlier because Source-1 masked it. The peak in the GPS band comes from Source-2.

    On the second FCC trip to Moss Landing Harbor, the signal in the GPS band had dropped by 10 dB in the late morning. We decided to hunt for the source of of a higher-level signal just outside the GPS band. This is the line at about 1580 MHz shown in Figure 5. The combined group quickly located the source of this signal. Again the combined use of a spectrum analyzer and portable receivers with a narrow-beam antenna was important. We also monitored the frequency on the spectrum analyzer inside MBARI and relayed the current value to the field team by cell telephone.

    Authors Badger and McGill with a 13-element yagi antenna and communications receiver used in dockside search.
    Authors Badger and McGill with a 13-element yagi antenna and communications receiver used in dockside search.

    In the end, turning the power on and off to a few boats and correlating this with the RFI signal identified the culprit. It turned out to be a another commercially-available UHF/VHF television antenna on a boat, one dock over from Source-1. When it was turned off, only the line near 1580 MHz went away. Therefore we labeled this perpetrator as Source-3. This owner returned the unit to the place of purchase for a replacement.

    The FCC has determined that the preamplifiers in Source-3 and Source-1 came from the same factory, which sold units to at least four well-known U.S. brand names of consumer electronic equipment. The bad units apparently began with a design change in late 2000; the number of units sold is not known to the authors.

    Suspect Roundup. It is now clear that there were at least three signals capable of jamming GPS in the Moss Landing Harbor area. Two were located and removed by a coordinated effort of MBARI, NPS and the FCC.

    The FCC made a few more attempts to locate Source-2 during the summer, but its level was lower with the higher temperatures. In the fall of 2001, the FCC succeeded in locating Source-2. It again turned out to be a VHF/UHF television antenna with preamplifier.

    Calibration

    There were a large number of spectra taken in the MBARI office. The signal came in the DGPS reference station antenna and went through two splitters and one inline amplifiers in the approximately 80 meters of low loss cable before emerging in the engineering office. Rather than examining the individual elements, we decided to calibrate the entire system.

    A calibrated source was sent to a standard antenna about 2 meters from the antenna. The same analyzer used to acquire data on the RFI sources was configured as it had been for the experimental data. The antenna manufacturer supplied beam patterns for the antenna. In this way, the signals were now calibrated at the level outside of the antenna.

    There still is an uncertainty about the space loss and antenna beam pattern gain/loss for actual sources. The latter can be found for the signals located, but not unknown signals such as Source-2. Accordingly the data were calibrated as a power level at the outside of the MBARI antenna.

    Comparison to a RFI Specification

    The composite Figure 6 shows one spectra, now calibrated to dBm outside the antenna, and a specification for the RFI levels. This is the specification that aircraft GPS receivers used for GPS landing systems must meet. The values measured from several other spectra taken at MBARI have also been plotted on this figure. Clearly these signals were above the narrow band limits by amounts from 3 to 24 dB.

    Source-1 had the highest level at -96 dBm. Its location is known to have been 325 meters from the MBARI antenna. It was at an elevation angle of -2.5 degrees. While the beam pattern of Source-1 is unknown, if it were omni-directional, it would exceed this FAA specification at a range of 50 kilometers or more. It is known to have caused marine GPS receivers to lose lock out to 3 kilometers. The effective power of this source can only be bounded from the data available. It is at least a few milliwatts.

    Source-2 varied in frequency and level. While on top of the L1 frequency, it had a level of -106 dBm. Source-3 had a level at MBARI of -99 dBm. While it was about 12 MHz from the center of L1, the variation in manufacture is likely to have produced units with emissions much nearer L1.

    Conclusions

    In one small California harbor, at least three emitters capable of jamming commercial GPS receivers were present. Two were located and removed by the authors. They were active UHF/VHF TV antennas and appeared to have the same internal preamplifier. The FCC has located and removed the third.

    Locating these sources proved difficult. It required a spectrum analyzer with averaging capabilities on a broadband antenna to track the jammer frequency and a narrow-band portable receiver with a directional antenna to localize it. Even then, a power on/off test was needed to verify that the source had indeed been found.

    The existence of the jamming was well-known in Moss Landing Harbor, and reported at least once to appropriate agencies. However, the problem persisted until local engineers and scientist hunted down the worst offender. Clearly there was a system problem with reporting and removal of RFI sources. More education of harbor masters or some other change needs to be implemented to deal more quickly with this type of problem.

    Acknowledgement

    Gary Thurmond, a retired MBARI engineer, provided technical advice and participated in the location of Source-1 and took the aerial photograph of Moss Landing Harbor.

    James R. Clynch is a research professor at the Naval Postgraduate School in Monterey, California, and has worked for 30 years in the use of satellite navigation systems for precision positioning and to study propagation effects. He has a PhD from Brown University.

    Andrew A. Parker, Richard W. Adler, and Wilbur R. Vincent are research professors in the Department of Electrical and Computer Engineering at the Naval Postgraduate School. Their PhDs are from University of Maryland, Pennsylvania State University, and Michigan State University, respectively.

    Paul McGill is an electrical engineer and George Badger a microwave technician at the Monterey Bay Aquarium Research Institute.

    Manufacturers

    The MBARI differential station uses a Trimble RL 4000 GPS receiver. The waterfront search employed a Hewlett Packard 8562 spectrum analyzer and an An ICOM IC-R3 5 communications receiver. A Hewlett Packard 8562E spectrum analyzer was used at NPS to study the emissions. Trimble Navigation provided a beam pattern for the specific antenna used on the MBARI roof, and the antenna used for calibration.