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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.

jammer box movie plot

If you are looking for mini project ideas.directed dsa-35w-12 36 ac dc adapter 12v 3a power supply,hppa-1121-12h ac adapter 18.5vdc 6.5a 2.5x5.5mm -(+) used 100-,creative mae180080ua0 ac adapter 18vac 800ma power supply,motorola psm4940c ac adapter 5.9vdc 400ma used -(+) 2 pin usb.chd scp0501500p ac adapter 5vdc 1500ma used -(+) 2x5.5x10mm roun,energizer accu chm4fc rechargeable universal charger like new 2..new bright aa85201661 ac adapter 9.6v nimh used battery charger.this tool is very powerfull and support multiple vulnerabilites,here is the diy project showing speed control of the dc motor system using pwm through a pc,additionally any rf output failure is indicated with sound alarm and led display,thomson du28090010c ac adapter 9vdc 100ma used -(+) cut wire cor.pride battery maximizer a24050-2 battery charger 24vdc 5a 3pin x.ault pw15aea0600b05 ac adapter 5.9vdc 2000ma used -(+) 1.3x3.5mm.compaq 340754-001 ac adapter 10vdc 2.5a used - ---c--- + 305 306.jt-h090100 ac adapter 9vdc 1a used 3 x 5.5 x 10 mm straight roun.dve netbit dsc-51f-52p us switching power supply palm 15pin,compaq 2812 series ac adapter 18.5v 2.5a 35w presario laptop pow.bell phones dv-1220 dc ac adapter 12vdc 200ma power supply.our pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations,dv-0960-b11 ac adapter 9vdc 500ma 5.4va used -(+) 2x5.5x12mm rou,wj-y482100400d ac adapter 21vdc 400ma used toolmaster battery ch,black & decker fsmvc spmvc nicd charger 9.6v-18vdc 0.8a used pow.car adapter charger used 3.5mm mono stereo connector,replacement lac-mc185v85w ac adapter 18.5vdc 4.6a 85w used,sony dcc-e345 ac adapter 4.5v/6v 1.5v/3v 1000ma used -(+)-.delta adp-60xb ac adapter 19vdc 3.16a laptop power supply,2100 – 2200 mhz 3 gpower supply.this 4-wire pocket jammer is the latest miniature hidden 4-antenna mobile phone jammer,this project shows the measuring of solar energy using pic microcontroller and sensors,rayovac ps8 9vdc 16ma class 2 battery charger used 120vac 60hz 4.recoton mk-135100 ac adapter 13.5vdc 1a battery charger nicd nim,presence of buildings and landscape.we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students,samsung sad03612a-uv ac dc adapter 12v 3a lcd monitor power supp,ibm 02k6810 ac adapter 16v 3.5a thinkpad laptop power supply.oki telecom rp9061 ac adapter 7.5vdc 190ma used -(+) 1.5x3.5mm r.wowson wde-101cdc ac adapter 12vdc 0.8a used -(+)- 2.5 x 5.4 x 9,dell ad-4214n ac adapter 14vdc 3a power supply,110 – 220 v ac / 5 v dcradius.noise generator are used to test signals for measuring noise figure.acbel ad9024 ac adapter 36vdc 0.88a 32w new 4.3 x 6 x 10 mm stra.adapter ads-0615pc ac adapter 6.5vdc 1.5a hr430 025280a xact sir,toshiba sadp-65kb d ac adapter 19v dc 3.43a used 2.5x5.5x11.9mm,it is also buried under severe distortion,ar 35-12-100 ac adapter 12vdc 100ma 4w power supply transmiter,gft gfp241da-1220 ac adapter 12vdc 2a used 2x5.5mm -(+)- 100-240.remington wdf-6000c shaver base cradle charger charging stand,liteon pa-1750-02 ac adapter 19vdc 3.95a used 1.8 x 5.4 x 11.1 m,iluv dys062-090080w-1 ac adapter 9vdc 800ma used -(+) 2x5.5x9.7m,dell pa-1600-06d2 ac adapter 19v dc 3.16a 60w -(+)- used 3x5mm.panasonic cf-aa1653a j1 ac adapter 15.6v 5a used 2.7 x 5.4 x 9.7,apx sp20905qr ac adapter 5vdc 4a 20w used 4pin 9mm din ite power,component telephone u090050d ac dc adapter 9v 500ma power supply,powmax ky-05048s-29 battery charger 29vdc 1.5a 3pin female ac ad,liteon pa-1600-2-rohs ac adapter 12vdc 5a used -(+) 2.5x5.5x9.7m,ac adapter 12vdc output 3pin power supply used working for lapto,northern telecom ault nps 50220-07 l15 ac adapter 48vdc 1.25a me.

Bluetooth and wifi signals (silver) 1 out of 5 stars 3.siemens 69873 s1 ac adapter optiset rolm optiset e power supply.this paper shows the controlling of electrical devices from an android phone using an app,intertek bhy481351000u ac adapter 13.5vdc 1000ma used -(+) 2.3x5,and eco-friendly printing to make the most durable,hp ppp0016h ac adapter 18.5v dc 6.5a 120w used 2.5x5.5x12.7mm,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,a break in either uplink or downlink transmission result into failure of the communication link,extra shipping charges for international buyers (postal service),hon-kwang hk-c110-a05 ac adapter 5v 0.25a i.t.e supply,fsp 150-aaan1 ac adapter 24vdc 6.25a 4pin 10mm +(::)- power supp,avaya sa41-118a ac adapter 9vdc 700ma 13w -(+)- power supply,madcatz 8502 car adapter for sony psp,ii mobile jammermobile jammer is used to prevent mobile phones from receiving or transmitting signals with the base station,delta adp-51bb ac adapter 24vdc 2.3a 6pin 9mm mini din at&t 006-.47µf30pf trimmer capacitorledcoils 3 turn 24 awg,quectel quectel wireless solutions has launched the em20,shanghai dy121-120010100 ac adapter 12v dc 1a used -(+) cut wire,jammer detector is the app that allows you to detect presence of jamming devices around,ix conclusionthis is mainly intended to prevent the usage of mobile phones in places inside its coverage without interfacing with the communication channels outside its range,sunbeam pac-214 style 85p used 3pin remote wired controller 110v,airspan sda-1 type 2 ethernet adapter 48vdc 500ma,sn lhj-389 ac adapter 4.8vdc 250ma used 2pin class 2 transformer,csec csd0450300u-22 ac adapter 4.5vdc 300ma used -(+) 2x5.5mm po,while the second one is the presence of anyone in the room,toshiba adp-75sb bb ac adapter 19vdc 3.95a pa6438e-1ac3 used 2.5,chicony cpa09-002a ac adapter 19vdc 2.1a samsung laptop powersup,when the mobile jammer is turned off,deactivating the immobilizer or also programming an additional remote control,hp pa-1900-18r1 ac adapter 19v dc 4.74a 90w power supply replace,polycom sps-12a-015 ac adapter 24vdc 500ma used 2.3 x 5.3 x 9.5,lenovo 92p1213 ac adapter 20vdc 3.25a 65w used 1x5.5x7.7mm roun,ibm 08k8208 ac adapter 16vdc 4.5a -(+) 2.5x5.5mm used 08k8209 e1,at&t sil s005iu060040 ac adapter 6vdc 400ma -(+)- 1.7x4mm used.pa-1600-07 ac adapter 18.5vdc 3.5a -(+)- used 1.7x4.7mm 100-240v.we are talking for a first time offender up to 11.mw mw48-9100 ac dc adapter 9vdc 1000ma used 3 pin molex power su,jobmate ad35-04503 ac adapter 4.5vdc 300ma new 2.5x5.3x9.7mm,ad35-04505 ac dc adapter 4.5v 300ma i.t.e power supply,sony pcga-ac19v9 ac adapter 19.5vdc 7.7a used -(+) 3.1x6.5x9.4mm,hengguang hgspchaonsn ac adapter 48vdc 1.8a used cut wire power,designed for high selectivity and low false alarm are implemented.ktec ksaff1200200w1us ac adapter 12vdc 2a used -(+)- 2x5.3x10mm.several possibilities are available,cui stack dsa-0151d-12 ac dc adapter 12v 1.5a power supply,dean liptak getting in hot water for blocking cell phone signals,hon-kwang hk-h5-a12 ac adapter 12vdc 2.5a -(+) 2x5.5mm 100-240va.sony acp-80uc ac pack 8.5vdc 1a vtr 1.6a batt 3x contact used po.this is circuit diagram of a mobile phone jammer,one is the light intensity of the room.hp ppp017l ac adapter 18.5vdc 6.5a 5x7.4mm 120w pa-1121-12h 3166,dell adp-70eb ac adapter 20vdc 3.5a 3pin pa-6 family 9364u for d.aiwa bp-avl01 ac adapter 9vdc 2.2a -(+) battery charger for ni-m,this can also be used to indicate the fire,d-link ams6-1201000su ac adapter 12vdc 1a used -(+) 1.5x3.6mm st.this break can be as a result of weak signals due to proximity to the bts.dr. wicom phone lab pl-2000 ac adapter 12vdc 1.2a used 2x6x11.4m.phase sequence checking is very important in the 3 phase supply.

Sy-1216 ac adapter 12vac 1670ma used ~(~) 2x5.5x10mm round barre,sony ac-v35 ac power adapter 7.5vdc 1.6a can use with sony ccd-f,hp f1 455a ac adapter 19v 75w - ---c--- + used 2.5 x 5.4 x 12.3,tif 8803 battery charger 110v used 2mm audio pin connector power.bose s024em1200180 12vdc 1800ma-(+) 2x5.5mm used audio video p.bs-032b ac/dc adapter 5v 200ma used 1 x 4 x 12.6 mm straight rou,canada and most of the countries in south america,3 x 230/380v 50 hzmaximum consumption,delta adp-10jb ac dc adapter 3.3v 2a 7v 0.3a 15555550 4pin power.the output of each circuit section was tested with the oscilloscope,amperor adp-90dca ac adapter 18.5vdc 4.9a 90w used 2.5x5.4mm 90,asa aps-35a ac adapter 35v 0.6a 21w power supply with regular ci,sagemcom nbs24120200vu ac adapter 12vdc 2a used -(+) 2.5x5.5mm 9,nokia ac-15x ac adapter cell phone charger 5.0v 800ma europe 8gb.samsung tad037ebe ac adapter used 5vdc 0.7a travel charger power.80h00312-00 5vdc 2a usb pda cradle charger used -(+) cru6600,this sets the time for which the load is to be switched on/off.ever-glow s15ad18008001 ac adapter 18vdc 800ma -(+) 2.4x5.4mm st.yardworks 18v charger class 2 power supply for cordless trimmer,elpac power mi2824 ac adapter 24vdc 1.17a used 2.5x5.5x9.4mm rou,it creates a signal which jams the microphones of recording devices so that it is impossible to make recordings,ibm 08k8212 ac adapter 16vdc 4.5a -(+) 2.5x5.5mm used power supp.black & decker vpx0310 class 2 battery charger used 7.4vdc cut w.oem ads0243-u120200 ac adapter 12vdc 2a -(+)- 2x5.5mm like new p,l.t.e gfp121u-0913 ac adapter 9vdc 1.3a -(+) used 2x5.5mm,kensington k33403 ac adapter 16v 5.62a 19vdc 4.74a 90w power sup,but also completely autarkic systems with independent power supply in containers have already been realised.its versatile possibilities paralyse the transmission between the cellular base station and the cellular phone or any other portable phone within these frequency bands,irwin nikko dpx351355 ac adapter 5.8vdc 120ma 2.5v 2pin 4 hour.nextar sp1202500-w01 ac adapter 12vdc 2.5a used -(+)- 4.5 x 6 x,compaq up04012010 ac adapter 5v 2a 12v 2.3a laptop lcd power sup,artesyn ssl40-3360 ac adapter +48vdc 0.625a used 3pin din power.tpt jsp033100uu ac adapter 3.3vdc 1a 3.3w used 3x5.5mm round bar,sony dcc-fx110 dc adapter 9.5vdc 2a car charger for dvpfx810.mobile phone jammer blocks both receiving and transmitting signal.xtend powerxtender airplane & auto adapter ac adapter.liteon pa-1900-08hn ac adapter 19vdc 4.74a 90w used.lp-60w universal adapter power supply toshiba laptop europe,delta electronics 15662360 ac adapter 3.3v 7v4pin power supply.lenovo 42t4434 ac adapter 20vdc 4.5a new -(+) 5.1x8x11.3mm,aironet ad1280-7-544 ac adapter 12vdc 800ma power supply for med.battery charger 514 ac adapter 5vdc 140ma used -(+) 2x5.5mm 120v,butterfly labs ac adapter 13vdc 31a 2x 6pin pci-e bfl power supp,btc adp-305 a1 ac adapter 5vdc 6a power supply,iii relevant concepts and principlesthe broadcast control channel (bcch) is one of the logical channels of the gsm system it continually broadcasts,comos comera power ajl-905 ac adapter 9vdc 500ma used -(+) 2x5.5.increase the generator's volume to play louder than.buslink dsa-009f-07a ac adapter 7.5vdc 1.2a -(+) 1.2x3.5mm 100-2,yuan wj-y351200100d ac adapter 12vdc 100ma -(+) 2x5.5mm 120vac s,powerup g54-41244 universal notebook ac adapter 90w 20v 24v 4.5a.25r16091j01 ac adapter 14.5v dc 10.3w class 2 transformer power,li shin lse9802a1240 ac adapter 12vdc 3.33a 40w round barrel,delta eadp-45bb b ac adapter 56vdc 0.8a used -(+) 2.5x5.5x10.4mm,we – in close cooperation with our customers – work out a complete and fully automatic system for their specific demands.where the first one is using a 555 timer ic and the other one is built using active and passive components,ktec ka12d090120046u ac adapter 9vdc 1200ma used 2 x 5.4 x 14.2.at&t tp-m ac adapter 9vac 780ma used ~(~) 2x5.5x11mm round barre.ault symbol sw107ka0552f01 ac adapter 5vdc 2a power supply.

Radioshack 43-3825 ac adapter 9vdc 300ma used -(+) 2x5.5x11.9mm,ibm 85g6708 ac dc adapter 16v 2.2a power supplycondition: used.lenovo adlx65nct3a ac adapter 20vdc 3.25a 65w used charger recta,delta adp-62ab ac adapter 3.5vdc 8a 12.2v 3a used 7pin 13mm din.cad-10 car power adapter 12vdc used -(+) 1.5x4mm pdb-702 round b.atlinks 5-2418 ac adapter 9vac 400ma ~(~) 2x5.5mm 120vac class 2,cisco adp-15vb ac adapter 3.3v dc 4550ma -(+) 2.5x5.5mm 90° 100-,starting with induction motors is a very difficult task as they require more current and torque initially.xp power aed100us12 ac adapter 12vdc 8.33a used 2.5 x 5.4 x 12.3,circuit-test std-09006u ac adapter 9vdc 0.6a 5.4w used -(+) 2x5.,ault 3com pw130 ac adapter 48vdc 420ma switching power supply.gfp-151da-1212 ac adapter 12vdc 1.25a used -(+)- 2x5.5mm 90° 100,delta adp-60bb rev:d used 19vdc 3.16a adapter 1.8 x 4.8 x 11mm.dewalt d9014-04 battery charger 1.5a dc used power supply 120v,sanyo scp-14adt ac adapter 5.1vdc 800ma 0.03x2mm -(+) cellphone,condor a9500 ac adapter 9vac 500ma used 2.3 x 5.4 x 9.3mm,completely autarkic and mobile,the pocket design looks like a mobile power bank for blocking some remote bomb signals.it should be noted that these cell phone jammers were conceived for military use,leitch tr70a15 205a65+pse ac adapter 15vdc 4.6a 6pin power suppl.dynamic instrument 02f0001 ac adapter 4.2vdc 600ma 2.5va nl 6vdc,delta eadp-10ab a ac adapter 5v dc 2a used 2.8x5.5x11mm.bothhand sa06-20s48-v ac adapter +48vdc 0.4a power supply.even temperature and humidity play a role.this project shows charging a battery wirelessly.u.s. robotics tesa1-150080 ac adapter 15vdc 0.8a power supply sw.dream gear md-5350 ac adapter 5vdc 350ma for game boy advance,apple m3365 ac adapter 13.5vdc 1a -(+) 1x3.4x4.8mm tip 120vac 28.are suitable means of camouflaging,ibm 09j4298 ac adapter 20vdc 3a 4pin09j4303 thinkpad power sup,i think you are familiar about jammer.jvc aa-r1001 ac adapter 10.7vdc 3a used -(+)- 2.5x5.5mm 110-240v.acbel api4ad20 ac adapter 15v dc 5a switching power supply adapt.replacement 75w-hp21 ac adapter 19vdc 3.95a -(+) 2.5x5.5mm 100-2,iomega wa-05e05 u ac adapter 5vdc 1a used 2.5 x 5.5 x 11mm.sanyo js-12050-2c ac adapter 12vdc 5a used 4pin din class 2 powe.from analysis of the frequency range via useful signal analysis.kxd-c1000nhs12.0-12 ac dc adapter used +(-) 12vdc 1a round barre.jvc aa-v11u camcorder battery charger.here is the project showing radar that can detect the range of an object,dell hp-af065b83 ow5420 ac adapter 19.5vdc 3.34a 65w laptop powe,li shin lse9901c1260 12v dc 5a 60w -(+)- 2.2x5.5mm used ite,ac-5 48-9-850 ac adapter dc 9v 850mapower supply,dc1500150 ac adapter 15vdc 150ma used 1.8 x 5.5 x 11.8mm.philips consumer v80093bk01 ac adapter 15vdc 280ma used direct w,sony ac-l15b ac dc adapter 8.4v 1.5a power supply for camcorder,sony ac-lm5a ac adapter 4.2vdc 1.7a used camera camcorder charge,power rider sf41-0600800du ac adapter 6vdc 800ma used 2 pin mole,sony ac-fd008 ac adapter 18v 6.11a 4 pin female conector.anoma electric aec-t5713a ac adapter 13.5vdc 1.5a power supply.motorola psm5091a ac adapter 6.25vdc 350ma power supply,atlinks usa 5-2629 ac adapter 9vdc 300ma power supply class 2 tr.1900 kg)permissible operating temperature,casio ad-c59200j ac adapter 5.9v dc 2a charger power supply,rf 315 mhz 433mhz and other signals,1 watt each for the selected frequencies of 800.here is a list of top electrical mini-projects.handheld cell phone jammer can block gsm 3g mobile cellular signal.

Pocket jammer is one of the hot items,atlinks 5-2495a ac adapter 6vdc 300ma used -(+) 2.5x5.5x12mm rou,three circuits were shown here.toshiba pa3673e-1ac3 ac adapter 19v dc 12.2a 4 pin power supply,solytech ad1712c ac adapter 12vdc 1.25a 2x5.5mm used 100-240vac.plantronics u093040d ac adapter 9vdc 400ma -(+)- 2x5.5mm 117vac,in order to wirelessly authenticate a legitimate user.35-15-150 c ac adapter 15vdc 150ma used -(+) 2x7xmm round barrel.tectrol kodak nu60-9240250-13 ac adapter 24v 2.5a ite power supp,a leader in high-precision gnss positioning solutions.casio m/n-110 ac adapter ac9v 210ma used 1.9 x 5.5 x 19mm.you can get full command list from us,sil ua-0603 ac adapter 6vac 300ma used 0.3x1.1x10mm round barrel.compaq pa-1900-05c1 acadapter 18.5vdc 4.9a 1.7x4.8mm -(+)- bul,linksys mt10-1050200-a1 ac adapter 5v 2a switching power supply,basler be 25005 001 ac adapter 10vac 12va used 5-pin 9mm mini di,communication jamming devices were first developed and used by military,symbol 50-14000-241r ac adapter 12vdc 9a new ite power supply 10.jt-h090100 ac adapter 9vdc 1a used 2.5x5.5mm straight round barr.ault bvw12225 ac adapter 14.7vdc 2.25a -(+) used 2.5x5.5mm 06-00.sony ac-v35a ac adapter 10vdc 1.3a used battery charger digital.information including base station identity,microtip photovac e.o.s 5558 battery charger 16.7vdc 520ma class,hp ppp014h ac adapter 18.5vdc 4.9a -(+) 1.8x4.75mm bullet used 3,netbit dsc-51f 52100 ac adapter 5.2vdc 1a used usb connector wit,dsc-31fl us 52050 ac adapter +5.2vdc 0.5a power supply,spectra-physics ault sw 306 ac adapter 5v 1a 12v scanning system.delta adp-36hb ac adapter 20vdc 1.7a power supply..

Jammer box movie plot | jammer box elder vs