PO855349-Task 1.1.b: Summary of flight test at CfAR Oct …cradpdf.drdc-rddc.gc.ca/PDFS/unc218/p803328_A1b.pdf · PO855349-Task 1.1.b: Summary of flight test at CfAR Oct ... Task

Summary of Flight Test at CfAR Oct 27 2015

J. Bradley Nelson Aeromagnetic Solutions Incorporated Prepared By: Aeromagnetic Solutions Incorporated 2486 Orient Park Drive Gloucester, ON, Canada K1B 5L9

Contractor's Document Number: PO855349-Task 1.1.b Contract Project Manager: J. Bradley Nelson, 1-613-841-4640 PWGSC Contract Number: 2000263 CSA: Dr Zahir A. Daya, 613-990-0672

The scientific or technical validity of this Contract Report is entirely the responsibility of the Contractor and the contents do not necessarily have the approval or endorsement of the Department of National Defence of Canada.

Contract Report

DRDC-RDDC-2015-C335

October 2015

© Her Majesty the Queen in Right of Canada, as represented by the Minister of National Defence, 2015

© Sa Majesté la Reine (en droit du Canada), telle que représentée par le ministre de la Défense nationale,

2015

2486 Orient Park Drive, Gloucester, ON, Canada, K1B 5L9 1-613-841-4640; [email protected]

Aeromagnetic Solutions Incorporated

Summary of Flight Test at CfAR Oct 27 2015

J. Bradley Nelson

Date: Oct 2015

Contract #: 2000263

PO #: 855349

Report #: PO855349-Task 1.1.b

PO855349-Task 1.1.b: Summary of flight test at CfAR Oct 27 2015

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1. Meeting at CfAR facilities prior to flight test A meeting was held at the University of Victoria’s Centre for Aerospace Research (CfAR) on Tuesday Oct 27, 2015. Attendees were from CfAR, the Canadian Forces Maritime Experimental Test Range (CFMETR), MARPAC, and Aeromagnetic Solutions Incorporated. The list of attendees is given in Appendix A. The purpose of the meeting was to acquaint CFMETR and RCAF personnel with the facilities and capabilities of CfAR, and to become more familiar with the Brican TD100 unmanned air vehicle that we expect to fly at CFMETR in 2016. After the meeting the attendees witnessed a flight test of the TD100 and were able to ask detailed questions about the flight operations. A description of the flight test is given in Section 2. Jenner Richards gave an introduction to the facilities including personnel, in-house capabilities, partners for out-sourced manufacture, and an overview of various clients and projects they are involved with. In particular he described the work that Brican Flight Systems has contracted them to perform – mainly to integrate and tune a Piccolo autopilot in the TD100 and tune/evaluate the auto-land capability. Jenner indicated that Brican has funded them for approximately 10 hours of flight time beyond the initial pre-Piccolo integration flying plus static and dynamic testing that took place earlier this summer. Prior to the demonstration on October 27, they had only flown two missions (~ 2 hours total) for the purpose of tuning the auto-pilot. Terry Berkley asked Brad Nelson to give an overview of the entire program so that all the attendees knew the background to both CfAR’s work with the TD100 and how this fits together with the CFMETR flight trial in February 2016. I explained the MHP requirement for a long-endurance UAV to investigate possible long-range detection, DRDC’s discussions with both PMO-MHP and DNR regarding the requirements and concept of operations of such a MAD-UAV, and how the scope of this project is verify the building blocks that would go into such a system. Specifically DRDC needs to demonstrate:

1) a low magnetic noise UAV 2) launch from a ship and landing on some platform at sea 3) transfer of magnetic data from the UAV to the groundstation 4) sufficient endurance and speed to be tactically useful 5) noise reduction and detection of magnetic targets with the MAD-equipped UAV.

Everyone understood that this is by no means a test and evaluation of a fleet-ready system, it is merely a test of the basic functionality that such a system would eventually need. Because CFMETR has not conducted UAV operations at their range, but they hope to do so in the near future on a number of projects, Terry Berkley and Commander Rich then asked CfAR staff a number of detailed questions about flight operations, what SFOC’s CfAR holds, whether they can do beyond line-of sight operations, etc. Of particular interest was the issue of long-range operations, because although a UAV could still be in communication with a groundstation at CFMETR, it would most likely not be visible. Thus CFMTER may have to use chase helicopters or boats equipped with secondary groundstations or spotters to relay information to the ground controller. Jenner indicated that although they have an SFOC that extends over water, they would need to use a chase helicopter or boat with a groundstation to fulfill the “line-of-sight” requirement in their operating certificate. This led to the question of how far DRDC expects the TD100 to ever be away from the ship (and thus the groundstation) during the CFMETR trial in February. Brad Nelson indicated that the flight paths are expected to be parallel to the ship’s track out to offsets of perhaps 500 m, but the run-in and run-out


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should be ~ 1.5 km. Including room to turn on each end would give an operating box of approximately 5 km in length and 1 km in width centered about the ship’s position. The maximum distance from the ship would be slightly over 2.5 km. Although the UAV may be difficult to see with the naked eye at that distance, it can easily be tracked with binoculars. Consequently CFMETR staff did not believe that they would need a chase boat or helicopter. There was a general discussion of airspace safety, the requirement for NOTAMs, UAV flight altitudes, and whether a CFMETR helicopter should be deployed to keep small aircraft out of the area. Although CFMETR has had accidental intrusions into CYR107 in the past, they have always been above 1000 ft ASL where the pilot did not realize that a special NOTAM had been issued. The air charts are clearly marked indicating it is restricted airspace below 1000 ft ASL and they have not had any issues with intrusions in that airspace. If DRDC conduct the TD100 flight trials at CFMETR below 1000 ft ASL, then CFMETR does not believe they have any requirement at all to deploy their helicopter. Brad Nelson brought up the question of access to CFMETR, which is a DND-controlled area, to non-government contractors (Aeromagnetic Solutions Incorporated, CAE Ltd, Brican Flight Systems). Terry Berkley indicated that if the contractors hold a security clearance, or a reliability status screening, that they can submit a visit clearance request through the PWGSC Industrial Security Program. This is the normal route for non-government personnel to visit DND facilities and both Aeromagnetic Solutions Incorporated and CAE Ltd are familiar with the process. DRDC should confirm that Brican personnel hold reliability status screening certificates and are familiar with the PWGSC-ISP procedures for submitting a visit clearance. This can take some time and the success of the project is completely reliant on Brican personnel operating the UAV. After the meeting the CfAR personnel provided a tour of their facilities to the RCAF and CFMETR personnel. 2. Flight test The flight test was held at the same small operations area that Brad Nelson and Zahir Daya were shown in April 2015. The area is shown in Figure 1. Unfortunately the longest sides of the operational area are only about 700 m long so the straight and level segments of the flight were only about 500 m in length. The flight was done with a “bare” TD100 – that is there were no wingpods that will house the G824 magnetometers. These pods will significantly affect the flight drag and possibly the flight dynamics of the UAV. The main goals of the flight test were to further fine tune the auto-pilot to eliminate “snaking” or side-to-side over-correction of the auto-pilot as it tries to fly down a straight line that was seen in the previous flight, and to further tune the auto-landing system. The auto-landing system uses a real-time kinematic (RTK) differential GPS system to real-time corrected navigational data to the auto-pilot with an accuracy of 1 to 2 cm. Since an error in height of 20 cm would lead to an overshoot of the landing area by some 10-15 m at the glide ratio and landing speed of the TD100, this navigational accuracy is critical.


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Figure 1. CfAR Op Area #1 west of highway 17, approximately 11 km south of the Victoria airport.

Prior to the flight a “landing zone” equal in size to the Brican landing pad was set out on the ground and marked with tape. Cameras were set up to record the landing from two different angles. The GPS for the RTK system is installed in the groundstation and the GPS position and height of the landing pad was obtained by setting the UAV’s at the desired landing spot and averaging the two GPS readings for a many minutes to get the absolute accuracy required. The UAV was launched using the Brican launcher which was mounted on a small trailer as shown in Figure 2. For the CFMETR trial we expect to use the same launcher mounted in either the Stikine or the Sikanni, both of which are YPT 610 Class Torpedo and Ship Ranging Vessels (TSRV). They are 290 tonnes, and 109 ft in length. One of these two vessels was tied up at the dock when Brad Nelson and Zahir Daya visited CFMETR in April 2015. The CFMETR personnel attending this demonstration flight felt there would not be any difficult mounting the launcher on the deck of either ship, although some care must be taken to make sure it is securely fastened to the deck. This suggests that the launcher should be delivered to CFMETR two days prior to the trial to ensure it gets mounted properly. The winds were very calm during the flight trial – on the ground it was estimated at only 1 or 2 m/s but aloft the UAV was measuring 5 m/s winds. On the landing there were some gentle gusts exactly perpendicular to the landing zone.


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Figure 2. Loading the TD100 UAV onto the Brican launcher.

The flight speed during the trial was nominally 23 m/s (~ 40 knots) at the beginning, then reduced to 19 m/s (~ 35 knots). There was no testing done near the top speed of the UAV (estimated by CfAR personnel as 70 knots). According to CfAR personnel, Brican has not indicated that they wish to do high-speed testing with this airframe. This is unfortunate as the flight stability might be considerably different at higher speeds. On the other hand, the CFMETR trial will most likely be done with the gas engine and MAD-XR pod which will be a significantly different platform than this bare TD100 so perhaps such high-speed testing by CfAR would not be relevant. To the naked eye the UAV appeared very stable in flight. The heads-up display on the groundstation control indicated that there were pitches and rolls of perhaps 2 degrees during the straight and level flight that only lasted ~ 20-25 seconds. The bank angles during the turns were ~ 30 degrees and the “turn-in/turn-out” banking was very smooth without much overshoot. The groundstation displays indicated that ~ 95% of the data packet transfers were successful. Detailed analysis of the flight data is given in section 3. After about 45 minutes or an hour of flying completely on autopilot (control inputs to slow down or speed up from the ground station were issued from the controllers, but the pilot never took control of the UAV), the command to auto-land was issued. In order to bleed off enough speed and altitude, the engine was shut off with over a full circuit to go and it glided downward and turned the corners of the circuit. On the final approach, the auto-pilot logic determined that it was too high and off-track to hit the landing target. In response, the auto-pilot turned the engine back on, continued around the circuit, and set up for a second attempt at landing. This time it was much lower (and thus on the correct glide slope) and it glided towards the landing zone very smoothly. The UAV touched down about 1 m off the centerline of the landing zone and about 2 m from the front edge. It slid along the grass and ended up significantly beyond the official end of the landing zone but that is to be expected when there was so


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little friction on the damp grass. Brad Nelson took a video of the landing, as did CfAR personnel, and the version taken by Brad Nelson will be provided to DRDC and NRC. Of the three flights that CfAR has conducted with the TD100, the first landing overshot the landing zone significantly, but the second and third flights both touched down within the landing zone. On the first flight the auto-landing algorithm commanded the UAV to flare the when it was about 20 cm above the ground, causing the UAV to float and touch down well beyond the landing strip. On the second flight and third flights the algorithm did not command the UAV to flare and the landing were successful. CfAR believes that because the glide slope on final approach is so shallow that the only way to repeatedly touch down in the landing area is to avoid flaring. During the CFMETR test when the TD100 is expected to land on the inflatable pad on the barge, this will bring up a number of issues. First of all, the glide slope is very shallow so the CFMETR personnel recommend that all the guard rails be removed so that the UAV does not have to “hop” over a rail, then try to drop down onto the pad. Second, there must be a catchment system of some sort at the end of the landing pad (nets? A foam pad?) because if the UAV overshoots the pad for any reason, it will either side off the barge into the ocean, or it will be significantly damaged flying into a steel deck. Third, everything standing on the deck should be removed so that the landing area and landing approaches are completely free of impediments. At the moment there are structures related to torpedo launchers on the deck of the barge and CFMETR personnel have indicated they will be removed. Fourth, care must be taken in how the barge is moored. If the barge uses a single anchor for mooring, it will be swinging around on its anchor and be aligned with the wind. Landing into the wind instead of cross wind should improve the landing reliability unless it is really gusty, in which case the mission may be cancelled anyway. The alternative is to use a multi-anchor mooring so the barge heading doesn’t change very much. A tug from Victoria will be required to move the barge anyway so it may not require much more effort to put out a multi-anchor system to keep the barge steady. Terry Berkley indicated this was certainly possible, and not significantly more expensive than using a single mooring as the tug would most likely remain stationed at CFMETR for the week of the trial. (The cost of the tug was estimated at $10K for the week.) Another possibility that was not discussed with Terry would be having one person on the barge to re-orient the landing strip into the wind a few minutes prior to landing. Fourth, all of these solutions assume that the auto-landing system can be given both a fly-to-point and a heading to land on. A GPS antenna for RTK DGPS must be very close to the landing strip because if the barge is rolling or pitching by more than a few degrees, the height of the landing pad will vary by few cm from the edge and that will be critical That GPS data will have to be sent to the groundstation via a radio link which most likely will be on the ship as the pre-flight checks will be a lot easier if the groundstation and UAV/launcher are all near each other. However, that GPS provides only a fly-to-point, not a heading for the UAV to fly during land. Discussions with Jenner Richards confirmed that the auto-landing algorithm can, in effect, be given a heading on which to land by changing the position of the “5 m altitude decision waypoint”. That is, a second waypoint is provided backwards along the glide slope of the final approach and normally it is used by the auto-pilot to make a decision on whether the UAV is close enough to the desired glide slope


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that it will be able to hit the landing zone. That waypoint can be changed a few minutes prior to the actual landing, resulting in the entire landing pattern getting modified. This will require either two GPS units on the barge, or a person on the barge with some method of accurately determining the correct heading and relaying that information to the groundstation operator. The CFMETR personnel indicated that they do have multiple GPS units that they use to obtain ship heading , that they could be mounted on the barge, and that it can be sent via a radio link to the groundstation. Ideally they would prefer not to have anyone on the barge during landing, but it may be possible if safety protocols are followed. If multiple GPS units and their associated radio links have to be set up on the barge, this also suggests that all of the equipment should arrive at CFMETR several days before the flight trial so it can all be set up and thoroughly tested. In summary, the flight demonstration went well with the launch, landing, and in-flight control being very successful. However, it also pointed out the difficulties that will be encountered during the CFMETR test and the planning that will have to be done very carefully to ensure a successful trial. 3. Analysis of flight data Appendix B contains more detailed analysis and plots verifying the quality of the data. This section focuses on just the estimated magnetic noise that will be generated by the motion of the UAV. This noise will be caused by:

1) vertical movement of the UAV through the gradient in the ambient magnetic field (buffeting noise),

2) permanent and induced magnetization in the platform creating varying magnetic

fields at the magnetometer location as the UAV pitches, rolls, or yaws. The gradient of the ambient field can be quite large in some geological environments, but a good estimate is that the vertical gradient will be on the order of that due to the Earth’s core magnetic field, which is 0.03 nT/m. The magnetic noise this creates is simply the variation in the altitude of the UAV in meters multiplied by this gradient. Figure 3 shows the altitude data measured during the flight. Although there appears to be variation of several meters, it should be noted that the legs were only 20 seconds long and during turns the UAV did tend to lose altitude. Thus the actual changes in altitude during straight and level flight were less than it appears in Figure 3. Figure 4 shows the expected buffeting noise along a single leg without any turns.


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Figure 3. Altitude variations during the flight.

Figure 4. Buffeting noise along a single straight and level leg (no noise correction applied).


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Experiments on other MAD platforms have shown that a noise reduction factor of 5 can be obtained if variations of the platform altitude are simply multiplied by 0.03 nT/m and subtracted off of the measured total-field signal. Thus if such a buffeting noise model was applied, one would expect the residual to be ~ 1/5 of the levels shown in Figure 4. The noise due to pitching, rolling, and yawing can be estimated if the magnetic properties of each component of the UAV are known and the positions of those components on the UAV relative to the magnetometer are known. The noise model is given by the following equation: Noise = ∑CiAi

where Ci are the Tolles and Lawson coefficients (which take into account both the geometry and magnetic properties) and the Ai are given by A1 = L/He A2= T/He A3 = V/He A4 = L*L/He A5= L*T/He A6= L*V/He A7= T*T/He A8 = T*V/He A9 = V*V/He where L,T,V are the components of the Earth’s field as measured in the coordinates of the UAV (L=Longitudinal, T=Transverse, and V=vertical). The Tolles and Lawson coefficients due to each of the components of the UAV calculated in October 2013 are: C1= -3.52 C2 = -0.14 C3 = -1.97 C4 = -2.91/50000 C5 = 8.83/50000 C6 = 0.20/50000 C7 = 0.47/50000 C8 = 0.50/50000 C9 = -0.20/50000 . The (L,T,V) signals were not measured during this flight, but they can be derived from the pitch, roll, and heading data measured by the auto-pilot along with the strength, dip, and variation of the Earth’s magnetic field at the location of the test flight. These latter three values were not measured, but they will be very close to the values at the Victoria Geomagnetic Observatory located at the Victoria airport. These are:


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tfc=54000 nT

var=16.44 deg

dip=69.6 deg .

This method allows us to estimate the magnetic noise caused by pitching, rolling, and yawing motion of the aircraft. In addition, we can estimate the residual amount left over after standard Tolles and Lawson compensation using the rule of thumb that compensation provides a factor of 20 noise reduction for most airborne platforms. Figure 5 shows the results for a single leg. The black trace shows the magnetic noise generated by just the pitching, rolling, and yawing while the green trace is simply that same trace divided by 20 and represents the expected residual after Tolles and Lawson compensation.

Figure 5. Magnetic noise TFU generated by pitching, rolling and yawing along a single line (black). Vs.

estimate of the compensated residual after applying Tolles and Lawson compensation (green).

Finally, the residual after buffeting noise compensation and the residual after Tolles and Lawson compensation are compared in Figure 6 to determine which noise source is more important. The two residuals are very similar in amplitude and frequency content, indicating both are important for obtaining the lowest noise possible.


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Figure 6. Comparison of estimated residual noise after compensation (green) and residual noise after

vertical buffeting noise reduction (red).

In summary, this analysis predicts that the vertical buffeting and the rotational motion of the UAV will both produce noise of ~ 10 pT/√ Hz.


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Appendix A: List of attendees at the meeting at CfAR and flight demonstration

Name Organization Telephone email

Terry Berkley CFMETR 250-468-5004 [email protected]

Cdr Darren Rich CO/CFMETR 250-468-5011 [email protected]

Maj Stephen Melanson

RCAF - ACCE(P) 250-363-1051 [email protected]

Jenner Richards UVic-CfAR 250-516-1972 [email protected]

Afzal Suleman UVic-CfAR 250-888-5539 [email protected]

Eldad Alber UVic-CfAR 250-507-7758 [email protected]

Trent Nichols CFMETR 250-468-5054 [email protected]

Tim Funk RCAF 250-896-4273 [email protected]

Matthew Currie CFMETR 250-468-5080 [email protected]

Brad Nelson ASI 613-841-4640 (w) [email protected]

613-864-4640 (c)

mailto:[email protected]




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Appendix B: Detailed analysis of the flight data Filename: BRICAN FT03 (50Hz).log IDL routine used for analysis: CfAR_piccolo_analysis_Oct_2015.pro The initial analysis is to determine if there are any missing samples. First plot the recorded time to verify that it is monotonic and does not have any obvious problems.

The next plot shows the derivative of time = 1/sample rate. This indicates that the sample rate is 25 Hz, not 50 Hz as CfAR personnel led us to believe. Examination of the 0th column of the ASCII data in the file confirms that the sample rate is 25 Hz, not 50 Hz.


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The next two plots are of longitude vs. latitude, and North vs. East position for the entire flight. There is only an issue right at the end of the flight where it appears to jump sideways in an odd fashion. Most of the legs over-plot quite well, although the corners do show some variation. This is likely the effect of changing cross winds making the flight path not completely repeatable.


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The following plot shows the measured altitude over the entire flight.


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The PSD of the altitude data from DP 1001-51000 was calculated then multiplied by the vertical gradient of the Earth’s core field (0.03 nT/m) to estimate the buffeting noise due to vertical motion.


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The previous plot appears to show 150-200 pT/√Hz of buffeting noise below 0.2 Hz, but this is likely because much of the time the UAV was flying around corners and it may be less stable vertically when it is banked. The following plot shows the altitude variation along just a single leg (DP 2001-2600).

To estimate the buffeting noise in straight and level flight, the data shown in the last plot were multiplied by the vertical gradient of the Earth’s core field (0.03 nT/m). The time series is shown in the following plot, and the PSD of that data is shown in the plot after that.


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This suggests the buffeting noise in straight and level flight will be more like 50 pT/√ Hz at the lower end of the MAD band which is acceptable. The magnetic noise should correlate well with variations in the altitude so the new algorithms that CAE has been contracted to include in their real-time signal


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processing suite should remove much of this noise. Analysis of other data sets on other projects suggests that a rule-of-thumb for buffeting noise removal is ~ a factor of 5. The synthetic L,T,V magnetometer signals were computed from the measured pitch, roll, and heading data, and the following Earth field parameters which were taken from the nearby Victoria BC geomagnetic observatory: tfc=54000 nT var=16.44 deg dip=69.6 deg. The following plot shows the synthetic T,L,V magnetometer signals calculated from the flight data.

The IDL procedure estimate_SL_noise.pro along with the Tolles and Lawson coefficients estimated in the Oct 2013 analysis of the components of the TD100 to calculate what the uncompensated magnetic noise will be had a magnetometer been installed on the wingtips of the TD100 during this flight. The next plot shows this (unfiltered) noise, which we shall denote TFU, in black. The noise reduction factor for Tolles and Lawson compensation algorithms is typically 20. The green trace in this plot is simply the black trace divided by 20, and it represents the estimate of the residual noise after compensation (denoted TFC).


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The power spectral densities of the data shown in the previous plot were calculated and are shown in the following plot. Note these power spectra were also calculated over DP 1001-51000 to avoid the ascent and descent stages of the flight.


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The noise appears to be ~ 100 pT/√Hz, but just as with the buffeting noise calculation, much of the manoeuvre noise is due to the large bank angles in turns. If we focus just on a single leg (DP 2001-2600), the time series for TFU vs. TFC looks like this

and the PSD’s look like this


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Notice that the noise appears to rise dramatically below 0.1 Hz, but remember that the legs were only 20 seconds long so much of that low-frequency noise is due to the large rolls during the turns. If the legs were 200 seconds long instead of 20 seconds, the spectrum would be much flatter down to 0.01 Hz. Finally, the residual noise due to the vertical buffeting (assuming the 5x reduction factor) and the noise due to the platform rotations (with the 20 x compensation factor) can be compared to determine which noise source will be more important. The green trace in the following plot is TFC (exactly the same as in the previous plot), while the red trace represents residual after buffeting noise reduction. They appear to be very similar in amplitude and frequency content, indicating that both sources are important.


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In summary, this analysis predicts that the vertical buffeting and the rotational motion of the UAV will produce broadband noise of roughly 10 pT/√ Hz.

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PO855349-Task 1.1.b: Summary of flight test at CfAR Oct …cradpdf.drdc-rddc.gc.ca/PDFS/unc218/p803328_A1b.pdf · PO855349-Task 1.1.b: Summary of flight test at CfAR Oct ... Task