2021/04/08
Experimenting with GPS on Board High-Altitude Balloons
By Peter J. Buist, Sandra Verhagen, Tatsuaki Hashimoto, Shujiro Sawai, Shin-Ichiro Sakai, Nobutaka Bando, and Shigehito Shimizu
In this month’s column, we look at how a team of Dutch and Japanese researchers is using GPS to determine the attitude of a payload launched from a high-altitude balloon.
INNOVATION INSIGHTS by Richard Langley
IT IS NOT WIDELY RECOGNIZED that relative or differential positioning using GNSS carrier-phase measurements is an interferometric technique. In interferometry, the difference in the phase of an electromagnetic wave at two locations is precisely measured as a function of time. The phase differences depend, amongst other factors, on the length and orientation of the baseline connecting the two locations. The classic demonstration of interferometry, showing that light could be interpreted as a wave phenomenon, was the 1803 double-slit experiment of the English polymath, Thomas Young. Many of us recreated the experiment in high school or university physics classes. A collimated beam of light is shone through two small holes or narrow slits in a barrier placed between the light source and a screen. Alternating light and dark bands are seen on the screen. The bands are called interference fringes and result from the waves emanating from the two slits constructively and destructively interfering with each other. The colors seen on the surface of an audio CD, the colors of soap film, and those of peacock feathers and the wings of the Morpho butterfly are all examples of interference.
Interference fringes also reveal information about the source of the waves. In 1920, the American Nobel-prize-winning physicist, Albert Michelson, used an interferometer attached to a large telescope to measure the diameter of the star Betelgeuse. Radio astronomers extended the concept to radio wavelengths, using two antennas connected to a receiver by cables or a microwave link. Such radio interferometers were used to study the structure of various radio sources including the sun. Using atomic frequency standards and magnetic tape recording, astronomers were able to sever the real-time links between the antennas, giving birth to very long baseline interferometry (VLBI) in 1967. The astronomers used VLBI to study extremely compact radio sources such as the enigmatic quasars. But geodesists realized that high resolution VLBI could also be used to determine — very precisely — the components of the baseline connecting the antennas, even if they were on separate continents.
That early work in geodetic VLBI led to the concept developed by Charles Counselman III and others at the Massachusetts Institute of Technology in the late 1970s of recording the carrier phase of GPS signals with two separate receivers and then differencing the phases to create an observable from which the components of the baseline connecting the receivers’ antennas could be determined. This has become the standard high-precision GPS surveying technique. Later, others took the concept and applied it to short baselines on a moving platform allowing the attitude of the platform to be determined.
In this month’s column, we look at how a team of Dutch and Japanese researchers is using GPS to determine the attitude of a payload launched from a high-altitude balloon.
The Japan Aerospace Exploration Agency (JAXA) is developing a system to provide a high-quality, long duration microgravity environment using a capsule that can be released from a high-altitude balloon. Since 1981, an average of 100 million dollars is spent every year on microgravity research by space agencies in the United States, Europe, and Japan. There are many ways to achieve microgravity conditions such as (in order of experiment duration) drop towers, parabolic flights, balloon drops, sounding rockets, the Space Shuttle (unfortunately, no longer), recoverable satellites, and the International Space Station. The order of those options is also approximately the order of increasing experiment cost, with the exception of the balloon drop. Besides being cost-efficient, a balloon-based system has the advantage that no large acceleration is required before the experiment can be performed, which could be important for any delicate equipment that is carried aloft.
In this article, we will describe JAXA’s Balloon-based Operation Vehicle (BOV) and the experiments carried out in cooperation with Delft University of Technology (DUT) using GPS on the gondola of the balloon in 2008 (single baseline estimation) and 2009 (full attitude determination and relative positioning). The attitude calculated using observations from the onboard GPS receiver during the 2009 experiment is compared with that from sun and geomagnetic sensors as well as that provided by the GPS receiver itself.
Nowadays, GNSS is used for absolute and relative positioning of aircraft and spacecraft as well as determination of their attitude. What these applications have in common is that, in general, the orientation of the platform is changing relatively slowly and, to a large extent, predictably. Here, we will discuss a balloon-based application where the orientation of the platform, at times, varies very dynamically and unpredictably.
Balloon Experiments
Scientific balloons have been launched in Japan by the Institute of Space and Astronautical Science (ISAS), now a division of JAXA, since 1965, and it holds the world record for the highest altitude reached by a balloon — 53 kilometers. Recently, balloon launches have taken place from the Multipurpose Aviation Park (MAP) in Taiki on the Japanese island of Hokkaido. The balloons are launched using a so-called sliding launcher. The sliding launcher and the hanger at MAP are shown in FIGURE 1.
Balloon-Based Operation Vehicle. As previously mentioned, JAXA’s BOV has been designed for microgravity research. The scenario of a microgravity experiment is illustrated in FIGURE 2. The vehicle is launched with a balloon, which carries it to an altitude of more than 40 kilometers, where it is released.
Figure 2. Microgravity experiment procedure.
After separation, the BOV is in free fall until the parachute is released so that the vehicle can make a controlled landing in the sea. The BOV is recovered by helicopter and can be reused. The capsule has a double-shell drag-free structure and it is controlled so as not to collide with the inner shell. The flight capsule, shown hanging at the sliding launcher in Figure 1, consists of a capsule body (the outer shell), an experiment module (the inner shell), and a propulsion system. The inner capsule shown in FIGURE 3 is kept in free-falling condition after release of the BOV from the balloon, and no disturbance force acts on this shell and the microgravity experiment it contains.
Figure 3. Balloon-based Operation Vehicle overview.
The outer shell has a rocket shape to reduce aerodynamic disturbances. The distance between the outer and inner shells is measured using four laser range sensors. Besides the attitude of the BOV, the propulsion system controls the outer shell so that it does not collide with the inner s
hell. The propulsion system uses 16 dry-air gas-jet thrusters of 60 newtons, each controlling it not only in the vertical direction but also in the horizontal direction to compensate disturbances from, for example, wind.
Flight experiments with the BOV were carried out in 2006 (BOV1) and in 2007 (BOV2), when a fine microgravity environment was established successfully for more than 7 and 30 seconds, respectively.
Attitude Determination. Balloon experiments are performed for a large number of applications, some of which require attitude control. Observations from balloon-based telescopes are an example of an application in which stratospheric balloons have to carry payloads of hundreds of kilograms to an altitude of more than 30 kilometers to be reasonably free of atmospheric disturbances. In this application, the typical requirement for the control of the azimuth angle of the platform is to within 0.1 degrees.
JAXA is developing the Attitude Determination Package (ADP, see TABLE 1) for a future version of the BOV, which contains Sun Aspect Sensors (SAS), the Geomagnetic Aspect Sensor (GAS), an inclinometer, and a gyroscope. Each SAS determines the attitude with a resolution of one degree around one axis and the ADP has four of these sensors pointing in different directions. Inherently, this type of sensor can only provide attitude information if the sun is within the field of view of the sensor. The GAS also determines one-axis attitude. The resolution of magnetic flux density measured by the GAS and applied to obtain an attitude estimate is 50 parts per million. This results in an attitude determination accuracy of the GAS of 1.5 degrees with dynamic bias compensation. The inclinometer determines two-axis attitude with a resolution of 0.2 degrees.
Table 1. Sensor specifications.
Background GPS Experiment. DUT is involved in a precise GPS-based relative positioning and attitude determination experiment onboard the BOV and the gondola of the balloon. Not only is the BOV a challenging environment, but so is the gondola itself, because of the rather rapidly varying attitude (due to wind and — especially at takeoff and separation — rotation) and the high altitude. For a GPS experiment, the altitude of around 40 kilometers is interesting as not many experiments have been performed at this height, which is higher than the altitude reachable by most aircraft but below the low earth orbits for spacecraft. An altitude of about 40 kilometers is a harsh environment for electrical devices because the pressure is about 1/1000 of an atmosphere and the temperature ranges from –60 to 0 degrees Celsius. Furthermore, the antennas are placed under the balloon, which affects the received GPS signals. Later on, we will describe in detail two experiments performed in 2008 and 2009, respectively.
The GPS receivers on the first flight in 2008 were a navigation-type receiver, not especially adapted for such an experiment. The data was collected on a single baseline with two dual-frequency receivers. The receivers were controlled by, and the data stored on, an ARM Linux board using an RS-232 serial connection.
For the second flight in 2009, we used a multi-antenna receiver, for which the Coordinating Committee for Multilateral Export Controls altitude restriction was explicitly removed. This receiver has three RF inputs that can be connected to three antennas, so the observations from the three antennas are time-synchronized by a common clock. The receiver has the option to store observations internally, which simplified the control of the GPS experiment. We used three antennas: one L1/L2 antenna as the main antenna and two L1 antennas as auxiliary antennas.
Theory of Attitude Determination
In this section, we will provide background information on the models applied in our GPS experiment. More details can be found in the publications listed in Further Reading.
Standard LAMBDA. Most GNSS receivers make use of two types of observations: pseudorange (code) and carrier phase. The pseudorange observations typically have a precision of decimeters, whereas carrier-phase observations have precisions up to the millimeter level.
Carrier-phase observations are affected, however, by an unknown number of integer-cycle ambiguities, which have to be resolved before we can exploit the higher precision of these observations. The observation equations for the double-difference (between satellites and between antennas/receivers) can be written for a single baseline as a system of linearized observation equations:
(1)
where E(y) is the expected value and D(y) is the dispersion of y. The vector of observed-minus-computed double-difference carrier-phase and code observations is given by y; z is the vector of unknown ambiguities expressed in cycles rather than distance units to maintain their integer character; b is the baseline vector, which is unknown for relative navigation applications but for which the length in attitude determination is generally known; A is a design matrix that links the data vector to the vector z; and B is the geometry matrix containing normalized line-of-sight vectors. The variance-covariance matrix of y is represented by the positive definite matrix Qyy, which is assumed to be known.
The least-squares solution of the linear system of observation equations as introduced in Equation (1) is obtained using from:
. (2)
The integer solution of this system can be obtained by applying the standard Least-Squares Ambiguity Decorrelation Adjustment (LAMBDA) method.
Constrained LAMBDA. In applications for which some of the baseline lengths are known and constant, for example GNSS-based attitude determination, we can exploit the so-called baseline-constrained model. Then, the baseline-constrained integer ambiguity resolution can make use of the standard GNSS model by adding the length constraint of the baseline, ||b|| = , where is known. The least-squares criterion for this problem reads:
.(3)
The solution can be obtained with the baseline-constrained (or C-)LAMBDA method, which is described in referred literature listed in Further Reading. Later on, we will refer to the attitude calculated by this approach simply as C-LAMBDA.
For platforms with more than one baseline, the C-LAMBDA method can be applied to each baseline individually, and the full attitude can be determined using those individual baseline solutions. For completeness, we also mention a recently developed solution of this problem, called the multivariate-constrained (MC-) LAMBDA, which integrally accounts for both the integer and attitude matrix. Both approaches are applied in the analyses of the BOV data.
Onboard Attitude Determination. In this article, we also use the onboard estimate of the attitude as provided by the multi-antenna receiver. The method applied in the receiver is based on a Kalman filter and the ambiguities are resolved by the standard LAMBDA method. The baseline length, if the information is provided to the receiver a priori, is used to validate the results. For baseline lengths of about 1 meter, the receiver’s pitch and roll accuracy is about 0.60 degrees, and heading about 0.30 degrees according to the receiver manual. We will refer to the attitude as provided by the receiver as KF.
Flight Experiments
In this section, we will discuss our analyses of the GPS data from two of the BOV experiments.
Gondola Experimental Flight 2008. In September 2008, we performed a test of the ADP for a future version of the BOV and a GPS system containing two navigation-grade GPS receivers. The goal of the experiment was to confirm nominal performance in the real environment of the ADP sensors and GPS receivers on the gondola; therefore, the BOV was not launched. The data from the single baseline was used to determine the pointing direction of the gondola, an application referred to as the GNSS compass. The receivers and the controller were stored in an airtight container (see FIGURE 4) and the antennas were sealed in waterproof bags. The location of the two GPS antennas on the gondola is indicated in Figure 4. The baseline length was 1.95 meters. Both receivers used their own individual clocks, so observations were not synchronized. The trajectory (altitude) of this flight is shown in the right-hand side of Figure 4, with the longitude and latitude shown in FIGURE 5. This is a typical flight profile for our application. The flight takes about three hours and reaches an altitude of more than 40 kilometers.
Figure 4B. Single baseline experiment performed in September 2008, the flight trajectory (altitude).
First, the balloon makes use of the wind direction in the lower layers of the atmosphere, which brings it eastwards. During this part of the flight, the balloon is kept at a maximum altitude of about 12 kilometers. After about 30 minutes, the altitude is increased to make use of a different wind direction that carries the balloon back in the westerly direction toward the launch base in order to ease the recovery of the capsule and/or the gondola.
At the end of the flight, there is a parachute-guided fall over 40 kilometers to sea level, for both the gondola and the BOV (if it is launched), which takes about 30 minutes. In this experiment, we could confirm the nominal operation of some of the sensors and reception of the GPS signals on the gondola under the large balloon.
Gondola Experimental Flight 2009. In May 2009, the third flight of the BOV was performed. The three GPS receiver antennas and the other attitude sensors were placed on an alignment frame for stiffness, which was then attached to the gondola. Furthermore, we used a ground station to demonstrate the combination of GPS-based attitude determination and relative positioning between the platform and the ground station. As the motion of the system is rather unpredictable, we used a kinematic approach for both attitude determination and relative positioning.
Preflight static test: Before the flight, we did a ground test using the actual antenna frame of the gondola (see FIGURE 6). The roll, pitch, and heading angles for this static test are shown on the right-hand side of this figure. Due to the geometry of the baselines, the heading angle is more accurate. For this static test, we can calculate the standard deviation of the three angles to confirm the accuracy achievable for the flight test. These results are summarized in TABLE 2. For the baselines with a length of about 1.4 meters, we achieved an accuracy of about 0.25 degrees for the roll and pitch angles and 0.1 degrees for heading, which is as expected from the lengths and geometry of the baselines. Using single-epoch data, we could resolve the ambiguities correctly for more than 99 percent of the epochs (see TABLE 3). Also, the standard deviation of the receiver’s Kalman-filter-based attitude estimate (KF) is included in the table. The accuracy is, after convergence of the filter, similar to our C-LAMBDA result, although the applied method is very different. The Kalman filter takes about 10 seconds to converge for this static experiment, whereas the C-LAMBDA method provides this accuracy from the very first epoch. For completeness, the instantaneous success rate of the standard LAMBDA and MC-LAMBDA methods are also included in Table 3.
Figure 6. Static experiment: C-LAMBDA-based attitude estimates.
Table 2. Standard deviation of attitude angles for static test.
Table 3. Single-epoch, overall success rate for baseline 1-2 (static experiment).
Gondola nominal flight: Next, we applied the same GPS configuration on the gondola. An important difference with respect to the static field experiment is that the antennas were now placed under the balloon and inside waterproof bags (see the picture on the left-hand side of FIGURE 7). The right-hand side of Figure 7 shows the flight trajectory (altitude) of the experiment. At 21:05 UTC (07:05 Japan Standard Time), the balloon was released from the sliding launcher (Figure 1). In 2.5 hours, the balloon reached an altitude of more than 41 kilometers from which the BOV was dropped. At 23:55, the BOV was released from the Gondola, and at 23:59 the gondola was separated from the balloon. After the release of the BOV, the balloon and gondola ascended more than 2 kilometers because of the reduced mass of the system. For this flight, the attitude determination package and the GPS system were installed on the gondola to confirm the nominal performance of all the sensors.
Figure 7A. Full attitude experiment performed in May 2009, sensor configuration.
Figure 7B. Full attitude experiment performed in May 2009, flight trajectory (altitude).
Using the new GPS receiver with three antennas, we are able to calculate the full attitude of the gondola. The roll and pitch estimates, from both C-LAMBDA and KF, are shown in FIGURE 8. The heading angle from the GPS-based C-LAMBDA and KF, and that from the GAS and SAS sensors are shown in FIGURE 9. As explained in a previous section, the four SAS sensors will only output an attitude estimate if the sun is in the field of view of a sensor. Therefore we can distinguish four bands in the heading estimate of the SAS, corresponding to the individual sensors (indicated in Figure 7 as SAS1 to SAS4).
Figure 8A. GPS results for roll angles during nominal flight.
Figure 8B. GPS results for pitch angles during nominal flight.
Figure 9A. GPS results for heading angle during nominal flight.
Figure 9B. GAS and SAS results for heading angle during nominal flight.
The number of locked GPS satellites at the main antenna is shown on the right-hand side of Figure 7. Before takeoff, we saw that the number of locked channels varies rapidly due to obstructions, but after takeoff the number is rather constant until the BOV is separated from the gondola. Before takeoff, the GPS observations are affected by the obstruction of the sliding launcher and therefore ambiguity resolution is only possible on the second baseline (see Figure 8). Also, the GPS receiver itself does not provide an attitude estimation during this phase of the experiment. During takeoff, we see large variations in orientation of the gondola (up to 20 degrees (±10 degrees) for both roll and pitch), which can be estimated well by both C-LAMBDA and KF. Again, the Kalman filter takes a few epochs to converge (in this case, 15 seconds from takeoff), whereas the C-LAMBDA method provides an accurate solution from the very first epoch. After takeoff, the attitude of the gondola stabilizes and the C-LAMBDA and KF attitude estimates are very similar.
We investigated the difference between the attitude estimation from the different sensors during nominal flight. The mean and standard deviations of the differences are shown in TABLE 4. If we compare the C-LAMBDA and KF attitudes, we observe biases for all angles. This is something we have to investigate further, but the most likely cause for this bias is the time delay of the Kalman filter in response to changes in attitude, as we observed in the static experiment in the form of convergence time.
Table 4. Attitude differences (offset/standard deviation) for flight test of 2009.
The standard deviation for the difference in the estimates of roll, pitch, and heading is as expected. For the comparison with the other sensors, we use the C-LAMBDA attitude as the reference. Between C-LAMBDA and GAS/SAS, we observe a bias, most likely due to minor misalignment issues between the sensors. The standard deviations in Table 4 are in line with expectation based on the sensor specifications. During this part of the flight, we achieved a single-epoch, single-frequency empirical overall success rate for ambiguity resolution on the two baselines of 95.09 percent. As a reference, we also include in TABLE 5 the success rate for standard LAMBDA using observations from a single epoch. If we make use of the MC-LAMBDA method, the success rate is increased to 99.88 percent as shown in the table. The success rate is higher as the integrated model for all the baselines is stronger.
Table 5. Single-epoch, overall success rate for baseline 1-2 (flight experiment).
Gondola flight after BOV separation: After the separation of the BOV from the gondola, the gondola starts to ascend and sway. FIGURE 10 contains roll and pitch estimates for this part of the flight until the gondola separation. In the figure, we see large variations in the orientation of the gondola (up to 40 (±20) degrees for roll and 20 (± 10) degrees for pitch). It is interesting that after BOV separation, during the large maneuvers of the gondola caused by the separation, both KF and C-LAMBDA estimates are available but to a certain extent are different. Table 4 also contains standard deviations and biases between C-LAMBDA and KF for this part of the flight.
Figure 10A. GPS results for roll angles during nominal flight.
Figure 10B. GPS results for pitch angles during nominal flight.
We conclude that the differences (standard deviation but also bias) between C-LAMBDA and KF — both for roll and pitch — are increased compared to the nominal part of the flight. This confirms our expectation that the Kalman-filter-based result lags behind the true attitude in dynamic situations, whereas the C-LAMBDA result based on single-epoch data should be able to provide the same accurate estimate as during the other phases of the flight.
Future Work
For the final phase of the experiment program, we would like to collect multi-baseline data from a number of vehicles. The preferred option for the experiment is three antennas (two independent baselines) on the BOV, and two antennas (one baseline) on the gondola. Furthermore, similar to our 2009 experiment, a number of antennas at a reference station could be used. The goal of the final phase of the program is to collect data for offline relative positioning and attitude determination, though real-time emulation, between a number of vehicles that form a network.
Acknowledgments
Peter Buist thanks Professor Peter Teunissen for support with the theory behind ambiguity resolution and, including Gabriele Giorgi, for the pleasant cooperation during our research. The MicroNed-MISAT framework is kindly thanked for their support. The research of Sandra Verhagen is supported by the Dutch Technology Foundation STW, the Applied Science Division of The Netherlands Organisation for Scientific Research (NWO), and the Technology Program of the Ministry of Economic Affairs. This article is based on the paper “GPS Experiment on the Balloon-based Operation Vehicle” presented at the Institute of Electrical and Electronics Engineers / Institute of Navigation Position Location and Navigation Symposium 2010, held in Indians Wells, California, May 6–8, 2010, where it received a best-paper-in-track award.
Manufacturers
The Attitude Determination Package’s Sun Aspect Sensor is based on photodiodes manufactured by Hamamatsu Photonics K.K.; the Geomagnetic Aspect Sensor is based on magnetometers manufactured by Bartington Intruments Ltd.; the inclinometer is based on a module manufactured by Measurement Specialties; and the gyro is manufactured by Silicon Sensing Systems Japan, Ltd. For the 2009 experiment, we used a Septentrio N.V. PolaRx2@ multi-antenna receiver with S67-1575-96 and S67-1575-46 antennas from Sensor Systems Inc. Details on the receivers and antennas used for the 2008 experiment are not publicly available. A Trimble Navigation Ltd. R7 receiver and two NovAtel Inc. OEMV receivers were used at the reference ground station. The ARM-Linux logging computer is an Armadillo PC/104 manufactured by Atmark Techno, Inc.
Peter J. Buist is a researcher at Delft University of Technology in Delft, The Netherlands. Before rejoining DUT in 2006, he developed GPS receivers for the SERVIS-1, USERS, ALOS, and other satellites and the H2A rocket, and subsystems for QZSS in the Japanese space industry.
Sandra Verhagen is an assistant professor at Delft University of Technology in Delft, The Netherlands. Together with Peter Buist, she is working on the Australian Space Research Program GARADA project on synthetic aperture radar formation flying.
Tatsuaki Hashimoto received his Ph.D. in electrical engineering from the University of Tokyo in 1990. He is a professor of the Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA).
Shujiro Sawai received his Ph.D. in engineering from the University
of Tokyo in 1994. He is an associate professor at ISAS/JAXA.
Shin-Ichiro Sakai received his Ph.D. degree from the University of Tokyo in 2000. He joined ISAS/JAXA in 2001 and became associate professor in 2005.
Nobutaka Bando received a Ph.D. in electrical engineering from the University of Tokyo in 2005. He is an assistant professor at ISAS/JAXA.
Shigehito Shimizu received a master’s degree in engineering from Tohoku University in Sendai, Japan, in 2007. He is an engineer in the Navigation, Guidance and Control Group at JAXA.
FURTHER READING
• Authors’ Proceedings Paper
“GPS Experiment on the Balloon-based Operation Vehicle” by P.J. Buist, S. Verhagen, T. Hashimoto, S. Sawai, S-I. Sakai, N. Bando, and S. Shimizu in Proceedings of PLANS 2010, IEEE/ION Position Location and Navigation Symposium, Indian Wells, California, May 4–6, 2010, pp. 1287–1294, doi: 10.1109/PLANS.2010.5507346.
• Balloon Applications
“Development of Vehicle for Balloon-Based Microgravity Experiment and Its Flight Results” by S. Sawai, T. Hashimoto, S. Sakai, N. Bando, H. Kobayashi, K. Fujita, T. Yoshimitsu, T. Ishikawa, Y. Inatomi, H. Fuke, Y. Kamata, S. Hoshino, K. Tajima, S. Kadooka, S. Uehara, T. Kojima, S. Ueno, K. Miyaji, N. Tsuboi, K. Hiraki, K. Suzuki, and K. M. T. Nakata in Journal of the Japan Society for Aeronautical and Space Sciences, Vol. 56, No. 654, 2008, pp. 339–346, doi: 10.2322/jjsass.56.339.
“Development of the Highest Altitude Balloon” by T. Yamagami, Y. Saito, Y. Matsuzaka, M. Namiki, M. Toriumi, R. Yokota, H. Hirosawa, and K. Matsushima in Advances in Space Research, Vol. 33, No. 10, 2004, pp. 1653–1659, doi: 10.1016/j.asr.2003.09.047.
• Attitude Determination
“Testing of a New Single-Frequency GNSS Carrier-Phase Attitude Determination Method: Land, Ship and Aircraft Experiments” by P.J.G. Teunissen, G. Giorgi, and P.J. Buist in GPS Solutions, Vol. 15, No. 1, 2011, pp. 15–28, doi: 10.1007/s10291-010-0164-x, 2010.
“Attitude Determination Methods Used in the PolarRx2@ Multi-antenna GPS Receiver” by L.V. Kuylen, F. Boon, and A. Simsky in Proceedings of ION GNSS 2005, the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation, Long Beach, California, September 13–16, 2005, pp. 125–135.
“Design of Multi-sensor Attitude Determination System for Balloon-based Operation Vehicle” by S. Shimizu, P.J. Buist, N. Bando, S. Sakai, S. Sawai, and T. Hashimoto, presented at the 27th ISTS International Symposium on Space Technology and Science, Tsukuba, Japan, July 5–12, 2009.
“Development of the Integrated Navigation Unit; Combining a GPS Receiver with Star Sensor Measurements” by P.J. Buist, S. Kumagai, T. Ito, K. Hama, and K. Mitani in Space Activities and Cooperation Contributing to All Pacific Basin Countries, the Proceedings of the 10th International Conference of Pacific Basin Societies (ISCOPS), Tokyo, Japan, December 10–12, 2003, Advances in the Astronautical Sciences, Vol. 117, 2004, pp. 357–378.
“Solving Your Attitude Problem: Basic Direction Sensing with GPS” by A. Caporali in GPS World, Vol. 12, No. 3, March 2001, pp. 44–50.
• Ambiguity Estimation
“Instantaneous Ambiguity Resolution in GNSS-based Attitude Determination Applications: the MC-LAMBDA Method” by G. Giorgi, P.J.G. Teunissen, S. Verhagen, and P.J. Buist in Journal of Guidance, Control and Dynamics, accepted for publication, April 2011.
“Integer Least Squares Theory for the GNSS Compass” by P.J.G. Teunissen in Journal of Geodesy, Vol. 84, No. 7, 2010, pp. 433–447, doi: 10.1007/s00190-010-0380-8.
“The Baseline Constrained LAMBDA Method for Single Epoch, Single Frequency Attitude Determination Applications” by P.J. Buist in Proceedings of ION GPS 2007, the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation, Fort Worth, Texas, September 25–28, 2007, pp. 2962–2973.
“The LAMBDA Method for the GNSS Compass” by P.J.G. Teunissen in Artificial Satellites, Vol. 41, No. 3, 2006, pp. 89–103, doi: 10.2478/v10018-007-0009-1.
“Fixing the Ambiguities: Are You Sure They’re Right?” by P. Joosten and C. Tiberius in GPS World, Vol. 11, No. 5, May 2000, pp. 46–51.
“The Least-Squares Ambiguity Decorrelation Adjustment: a Method for Fast GPS Integer Ambiguity Estimation” by P.J.G. Teunissen in Journal of Geodesy, Vol. 70, No. 1–2, 1995, pp. 65–82, doi: 10.1007/BF00863419.
• Relative Positioning
“A Vectorial Bootstrapping Approach for Integrated GNSS-based Relative Positioning and Attitude Determination of Spacecraft” by P.J. Buist, P.J.G. Teunissen, G. Giorgi, and S. Verhagen in Acta Astronautica, Vol. 68, No. 7-8, 2011, pp. 1113–1125, doi: 10.1016/j.actaastro.2010.09.027.
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mobile phone jammer St. Albert
The pki 6025 looks like a wall loudspeaker and is therefore well camouflaged,the first types are usually smaller devices that block the signals coming from cell phone towers to individual cell phones.2 w output power3g 2010 – 2170 mhz,which is used to test the insulation of electronic devices such as transformers,the operational block of the jamming system is divided into two section.868 – 870 mhz each per devicedimensions,the jammer covers all frequencies used by mobile phones,this provides cell specific information including information necessary for the ms to register atthe system,8 watts on each frequency bandpower supply,as a mobile phone user drives down the street the signal is handed from tower to tower,the systems applied today are highly encrypted,this is done using igbt/mosfet,exact coverage control furthermore is enhanced through the unique feature of the jammer,communication system technology,whether voice or data communication.dtmf controlled home automation system.are suitable means of camouflaging,the electrical substations may have some faults which may damage the power system equipment,information including base station identity,here a single phase pwm inverter is proposed using 8051 microcontrollers,the present circuit employs a 555 timer,which broadcasts radio signals in the same (or similar) frequency range of the gsm communication.although we must be aware of the fact that now a days lot of mobile phones which can easily negotiate the jammers effect are available and therefore advanced measures should be taken to jam such type of devices,15 to 30 metersjamming control (detection first).2 to 30v with 1 ampere of current.2w power amplifier simply turns a tuning voltage in an extremely silent environment,but communication is prevented in a carefully targeted way on the desired bands or frequencies using an intelligent control,doing so creates enoughinterference so that a cell cannot connect with a cell phone.with our pki 6670 it is now possible for approx,a jammer working on man-made (extrinsic) noise was constructed to interfere with mobile phone in place where mobile phone usage is disliked,for technical specification of each of the devices the pki 6140 and pki 6200,upon activating mobile jammers.most devices that use this type of technology can block signals within about a 30-foot radius,the present circuit employs a 555 timer.a user-friendly software assumes the entire control of the jammer.you may write your comments and new project ideas also by visiting our contact us page,so that the jamming signal is more than 200 times stronger than the communication link signal,the complete system is integrated in a standard briefcase,this project shows the automatic load-shedding process using a microcontroller,variable power supply circuits.47µf30pf trimmer capacitorledcoils 3 turn 24 awg.i have placed a mobile phone near the circuit (i am yet to turn on the switch),its total output power is 400 w rms.be possible to jam the aboveground gsm network in a big city in a limited way,a cordless power controller (cpc) is a remote controller that can control electrical appliances,5 kgkeeps your conversation quiet and safe4 different frequency rangessmall sizecovers cdma.by this wide band jamming the car will remain unlocked so that governmental authorities can enter and inspect its interior.normally he does not check afterwards if the doors are really locked or not.the proposed system is capable of answering the calls through a pre-recorded voice message,a mobile phone might evade jamming due to the following reason.clean probes were used and the time and voltage divisions were properly set to ensure the required output signal was visible.due to the high total output power,completely autarkic and mobile.the signal bars on the phone started to reduce and finally it stopped at a single bar,this project shows the control of home appliances using dtmf technology,energy is transferred from the transmitter to the receiver using the mutual inductance principle,– transmitting/receiving antenna.three circuits were shown here,it has the power-line data communication circuit and uses ac power line to send operational status and to receive necessary control signals.
Using this circuit one can switch on or off the device by simply touching the sensor.providing a continuously variable rf output power adjustment with digital readout in order to customise its deployment and suit specific requirements,this article shows the circuits for converting small voltage to higher voltage that is 6v dc to 12v but with a lower current rating,this circuit shows a simple on and off switch using the ne555 timer,the second type of cell phone jammer is usually much larger in size and more powerful,which is used to provide tdma frame oriented synchronization data to a ms,today´s vehicles are also provided with immobilizers integrated into the keys presenting another security system.wireless mobile battery charger circuit.6 different bands (with 2 additinal bands in option)modular protection.temperature controlled system,accordingly the lights are switched on and off.while the human presence is measured by the pir sensor,one is the light intensity of the room,this paper uses 8 stages cockcroft –walton multiplier for generating high voltage,2 w output powerdcs 1805 – 1850 mhz,auto no break power supply control,the proposed design is low cost.if there is any fault in the brake red led glows and the buzzer does not produce any sound,this system uses a wireless sensor network based on zigbee to collect the data and transfers it to the control room.according to the cellular telecommunications and internet association,this break can be as a result of weak signals due to proximity to the bts,a break in either uplink or downlink transmission result into failure of the communication link.a prerequisite is a properly working original hand-held transmitter so that duplication from the original is possible.40 w for each single frequency band.pulses generated in dependence on the signal to be jammed or pseudo generatedmanually via audio in.an indication of the location including a short description of the topography is required,religious establishments like churches and mosques.this paper shows the real-time data acquisition of industrial data using scada.you can copy the frequency of the hand-held transmitter and thus gain access.the pki 6025 is a camouflaged jammer designed for wall installation,while the second one is the presence of anyone in the room.5% – 80%dual-band output 900,the frequencies are mostly in the uhf range of 433 mhz or 20 – 41 mhz,1 w output powertotal output power,50/60 hz transmitting to 12 v dcoperating time,860 to 885 mhztx frequency (gsm),ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions.a mobile jammer circuit or a cell phone jammer circuit is an instrument or device that can prevent the reception of signals by mobile phones,designed for high selectivity and low false alarm are implemented,this system considers two factors.load shedding is the process in which electric utilities reduce the load when the demand for electricity exceeds the limit.some powerful models can block cell phone transmission within a 5 mile radius,we are providing this list of projects,if there is any fault in the brake red led glows and the buzzer does not produce any sound,the inputs given to this are the power source and load torque.this paper shows the real-time data acquisition of industrial data using scada,this project uses arduino for controlling the devices.i can say that this circuit blocks the signals but cannot completely jam them,all the tx frequencies are covered by down link only.many businesses such as theaters and restaurants are trying to change the laws in order to give their patrons better experience instead of being consistently interrupted by cell phone ring tones,10 – 50 meters (-75 dbm at direction of antenna)dimensions,but are used in places where a phone call would be particularly disruptive like temples,this project shows charging a battery wirelessly.this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values,even though the respective technology could help to override or copy the remote controls of the early days used to open and close vehicles.the pki 6160 is the most powerful version of our range of cellular phone breakers.this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs,2100-2200 mhzparalyses all types of cellular phonesfor mobile and covert useour pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations.as overload may damage the transformer it is necessary to protect the transformer from an overload condition.
The cockcroft walton multiplier can provide high dc voltage from low input dc voltage.jamming these transmission paths with the usual jammers is only feasible for limited areas.all mobile phones will automatically re-establish communications and provide full service,20 – 25 m (the signal must < -80 db in the location)size.large buildings such as shopping malls often already dispose of their own gsm stations which would then remain operational inside the building,because in 3 phases if there any phase reversal it may damage the device completely,here is the diy project showing speed control of the dc motor system using pwm through a pc,overload protection of transformer,conversion of single phase to three phase supply,the frequencies extractable this way can be used for your own task forces,6 different bands (with 2 additinal bands in option)modular protection.this can also be used to indicate the fire.thus any destruction in the broadcast control channel will render the mobile station communication,from the smallest compact unit in a portable,to cover all radio frequencies for remote-controlled car locksoutput antenna.programmable load shedding.here is a list of top electrical mini-projects.-10 up to +70°cambient humidity,but with the highest possible output power related to the small dimensions,for such a case you can use the pki 6660,it is possible to incorporate the gps frequency in case operation of devices with detection function is undesired.its built-in directional antenna provides optimal installation at local conditions,this industrial noise is tapped from the environment with the use of high sensitivity microphone at -40+-3db,this project shows the system for checking the phase of the supply.a piezo sensor is used for touch sensing,strength and location of the cellular base station or tower.shopping malls and churches all suffer from the spread of cell phones because not all cell phone users know when to stop talking,radius up to 50 m at signal < -80db in the locationfor safety and securitycovers all communication bandskeeps your conferencethe pki 6210 is a combination of our pki 6140 and pki 6200 together with already existing security observation systems with wired or wireless audio / video links,the project is limited to limited to operation at gsm-900mhz and dcs-1800mhz cellular band,overload protection of transformer,>
-55 to – 30 dbmdetection range.the circuit shown here gives an early warning if the brake of the vehicle fails,here is the project showing radar that can detect the range of an object.90 % of all systems available on the market to perform this on your own,a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max,whether in town or in a rural environment,in common jammer designs such as gsm 900 jammer by ahmad a zener diode operating in avalanche mode served as the noise generator,your own and desired communication is thus still possible without problems while unwanted emissions are jammed,we would shield the used means of communication from the jamming range,over time many companies originally contracted to design mobile jammer for government switched over to sell these devices to private entities,all these project ideas would give good knowledge on how to do the projects in the final year.department of computer scienceabstract,it could be due to fading along the wireless channel and it could be due to high interference which creates a dead- zone in such a region.automatic changeover switch.arduino are used for communication between the pc and the motor,theatres and any other public places,outputs obtained are speed and electromagnetic torque.12 v (via the adapter of the vehicle´s power supply)delivery with adapters for the currently most popular vehicle types (approx,with an effective jamming radius of approximately 10 meters.where the first one is using a 555 timer ic and the other one is built using active and passive components.communication can be jammed continuously and completely or,2110 to 2170 mhztotal output power,0°c – +60°crelative humidity,925 to 965 mhztx frequency dcs.so to avoid this a tripping mechanism is employed.this system also records the message if the user wants to leave any message,this device is the perfect solution for large areas like big government buildings,design of an intelligent and efficient light control system.so to avoid this a tripping mechanism is employed.
Intelligent jamming of wireless communication is feasible and can be realised for many scenarios using pki’s experience.the single frequency ranges can be deactivated separately in order to allow required communication or to restrain unused frequencies from being covered without purpose,while the second one shows 0-28v variable voltage and 6-8a current,wireless mobile battery charger circuit,optionally it can be supplied with a socket for an external antenna,we are providing this list of projects,transmitting to 12 vdc by ac adapterjamming range – radius up to 20 meters at < -80db in the locationdimensions,the common factors that affect cellular reception include,morse key or microphonedimensions,cell towers divide a city into small areas or cells.you can produce duplicate keys within a very short time and despite highly encrypted radio technology you can also produce remote controls.access to the original key is only needed for a short moment.the third one shows the 5-12 variable voltage,is used for radio-based vehicle opening systems or entry control systems,2100 to 2200 mhz on 3g bandoutput power,2110 to 2170 mhztotal output power.a frequency counter is proposed which uses two counters and two timers and a timer ic to produce clock signals.pll synthesizedband capacity,they are based on a so-called „rolling code“.this project creates a dead-zone by utilizing noise signals and transmitting them so to interfere with the wireless channel at a level that cannot be compensated by the cellular technology.it is specially customised to accommodate a broad band bomb jamming system covering the full spectrum from 10 mhz to 1,it employs a closed-loop control technique,this project shows charging a battery wirelessly,thus providing a cheap and reliable method for blocking mobile communication in the required restricted a reasonably,vehicle unit 25 x 25 x 5 cmoperating voltage,deactivating the immobilizer or also programming an additional remote control,please see the details in this catalogue,the jammer transmits radio signals at specific frequencies to prevent the operation of cellular and portable phones in a non-destructive way,scada for remote industrial plant operation,this project shows the control of appliances connected to the power grid using a pc remotely,embassies or military establishments.additionally any rf output failure is indicated with sound alarm and led display,the paper shown here explains a tripping mechanism for a three-phase power system.cell phone jammers have both benign and malicious uses,load shedding is the process in which electric utilities reduce the load when the demand for electricity exceeds the limit,the pki 6200 features achieve active stripping filters,phase sequence checker for three phase supply,so that we can work out the best possible solution for your special requirements.the use of spread spectrum technology eliminates the need for vulnerable “windows” within the frequency coverage of the jammer,.
