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Copyright © 2008 The Boeing Company. All rights reserved.
Helicopter Flight Demonstration of Lunar and Planetary
Lander Technologies
Martin J. Bayer1
Boeing Phantom Works, Huntington Beach, CA 92647
Steve D. Berg2
Boeing Phantom Works, Tukwila, WA 98108
Mark Hardesty3
Boeing Integrated Defense Systems, Mesa, AZ 85215
In November 2007, Boeing performed a flight test campaign of sensor and avionics
technologies that are relevant for future lunar and planetary landers, using a helicopter test
platform called Unmanned Little Bird (ULB). Overall goals in addition to the specific
experiment objectives were to demonstrate the potential of the ULB to serve as an effective
sensors and systems test platform for space related applications, to demonstrate that rapid
ULB reconfiguration is possible in support of a highly productive test environment with new
experiments flown each day for several days in a row, and to examine the potential of using
the ULB as a lunar or Mars lander astronaut training aid for critical portions of the final
approach and landing phase. All experiments were successfully executed as planned and
yielded satisfactory to excellent results. This paper describes the main experiments that were
performed and the results that were achieved.
I. Introduction
This paper describes flight test activities, including associated objectives and results, which Boeing conducted in
November 2007 in Winslow, AZ, using the Boeing Unmanned Little Bird (ULB) MD-530-FF rotorcraft platform to
demonstrate various sensor, avionics and navigation related technologies of interest for potential applications in
future lunar landers. This specifically concerned the following technologies and operations:
• Lunar lander descent and final approach trajectory emulation
• Laser Detection and Ranging (LADAR) 3-D active imaging system
• Orbital Express sensor suite crater navigation passive imaging system
• Pseudolite radio beacon precision navigation system
The implementation of a cost-effective test approach aimed at enabling real-time realistic testing to increase the
Technology Readiness Level of these technologies in a stepwise approach for limiting risk exposure allows
mitigating potential technical, schedule and cost issues associated with future exploration missions, such as
precision lunar landings.
The demonstration campaign was performed to validate these technologies in a flight environment in real time,
and to later on also be able to evaluate and validate navigation algorithms and hazard detection and avoidance
capabilities. A further upgrade of the demonstrator approach could lead to a platform that is able to validate also the
guidance and possibly the control techniques or technologies in a closed loop configuration. An additional goal was
to examine the potential for using the Automated Flight Control System (AFCS) enabled ULB as a lunar or Mars
lander pilot training aid for critical portions of the final approach and landing phase.
1
Engineer, Advanced Technology Concepts, 5301 Bolsa Avenue, Mail Code H45N-E404, AIAA Member
2
Engineer, Advanced Technology Concepts, 9725 East Marginal Way South, Mail Code 42-52
3
Flight Test Engineer/Boeing Rotorcraft Unmanned Systems Test Director, Engineering Flight Test, 5000 East
McDowell Road, Mail Code M560-G023
AIAA SPACE 2008 Conference & Exposition
9 - 11 September 2008, San Diego, California
AIAA 2008-7803
Copyright © 2008 by The Boeing Company. All rights reserved. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.

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II. Unmanned Little Bird Helicopter Flight Test Platform
The flight tests for this series of demonstration flights were performed using the Boeing ULB helicopter as the
test bed platform. The ULB helicopter, as shown in Figure 1, is a modified MD-530-FF two seat (pilot plus
passenger) helicopter with the tail number N7032C.
Figure 1. Boeing MD-530FF Unmanned Little Bird in Autonomous Flight.
The ULB is a Boeing developed, owned and controlled fully instrumented Unmanned Aerial Vehicle (UAV)
test-bed aircraft using an Autonomous Flight Control System (AFCS) with optional capability for piloted flight.
Associated components include AFCS actuators, an AFCS Flight Control Computer (FCC), an Embedded Global
Positioning System (GPS)/Inertial Navigation System (INS) (EGI) navigation system, Air Data Computers (ADC), a
Wide Area Augmentation System (WAAS) and Real Time Kinematic (RTK) differentially enabled dual freqency
NovAtel GPS, a Tactical Common Data Link (TCDL), system interface displays, and a nose mounted WesCam
Turreted Sensor.
Figure 2 shows the typical maneuver capability. The ULB is also one of the few helicopters that have an
approved negative g capability.
Figure 2. Typical Unmanned Little Bird Maneuver Capability.

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Cruise speed in the demonstration configuration is estimated at 110 knots. Flight time is about 1 hour 40 minutes
with a standard fuel load, depending on payload mass. With an equipped empty weight of 2159 lbs, a crew of two
estimated at 200 lbs each and a full fuel load of 400 lbs, experimental equipment payload at sea level can range up to
550 lbs. The aircraft has an on board power supply of 28 V DC with 250-300 A available for payload applications.
The complete ULB system includes a ground control station for uncrewed flight and allows the quick integration
of different prototype subsystems. The ULB can be readily equipped with additional sensors, hard- and software,
which can be integrated with the existing on board systems. Data measurements can be either recorded and retrieved
after landing for post flight analyses or transmitted to the ground in real time via communications downlinks. The
ULB can be deployed for either crewed or uncrewed operation, and the ‘optionally crewed’ capability allows it to be
operated as a crewed platform to travel from an airfield through controlled airspace to a point of uncrewed use.
Pilots can therefore ferry the ULB aircraft directly to the deployment point and release the aircraft for subsequent
autonomous operation as a UAV while passively monitoring flight operations. This capability provides significant
test and operational benefits. The critical attribute of a manual over-ride by an on-board safety pilot allows operating
high dollar or one-of-a-kind prototype systems even with limited maturity and technology readiness on the ULB
platform at the corners of the flight envelope in civil airspace with minimum safety and software concerns.
The ULB represents an asset with low operational costs that can be easily repositioned to any unique test
environment or customer location to minimize travel or integration expenses. It provides the opportunity to explore
concepts of operations, and to rapidly install and evaluate the performance of a vast range of sensor, communication,
and navigation devices and systems. Data from these efforts can enable rapid prototyping decisions that can allow
hardware and software modifications in time to retest while still on test location. System tests requiring on-board
operator intervention to effect real-time tuning and data acquisition are easily accomplished using an installed touch
screen equipped cockpit monitor interfaced with a Windows XP based Panasonic Toughbook computer.
III. Overview of Test Campaign
The test campaign described in the following comprised the installation and in flight operation of a variety of
hard- and software elements and components on the ULB helicopter during several individual sorties for flight
evaluation and data collection. The ULB was reconfigured repeatedly for performing different experiments on
separate sorties, and it was flown in a number of different flight configurations, conditions and profiles that
addressed specific demonstration objectives. The internal test equipment was generally mounted in the aft passenger
compartment on special pallets, while sensors were mounted on the outside of the aircraft, either on a chin mount in
front, beneath the fuselage or on pylons on either side. INS and GPS signals required for precision position data
were made available for recording purposes by the on board equipment, and relevant flight test data files were
recorded on board and processed for subsequent evaluation.
All flight testing was conducted via manual pilot control under visual meteorological conditions during daylight
hours. A total of over 13 flight test hours were accumulated during 14 flights over a space of six days. Flights ranged
from approximately 10 minutes to 2 hours in duration. The test campaign was flown from the Charles Lindbergh
Regional Airport (INW) in Winslow, AZ. Being situated in the northern Arizona high desert, the area surrounding
Winslow includes a number of geological and topological features, such as canyons, rock and hill formations and
mesas, which readily lend themselves as similes for lunar or Martian terrain.
The details of the different lunar lander related flight test experiments and their main results are outlined in the
following.
A. Lunar Lander Trajectory Emulation
The objective of this experiment was to assess the applicability of the ULB as a demonstration as well as training
platform for future lunar landers. This entailed determining the compatibility of the ULB flight envelope and
performance parameters with typical lander trajectory profiles in real time. For this experiment, ULB GPS/INS
position data were determined and recorded, using available on board equipment.
Several slanted descent trajectories with different approach angles and near constant deceleration were manually
flown, and precision position data were successfully recorded. The final segments (approximately comprising the
last 30 seconds) of several generic lunar lander trajectories with different approach angles were thus successfully
emulated by the ULB under manual control. The approaches were executed in straight line descent maneuvers with
velocity decreasing approximately linearly over time, until the ULB arrived at low altitude above the assumed
landing spot at zero velocity. The main flight path parameters of the final approach phase of an example trajectory
are shown in Figure 3. The flown approaches validated the viability of the ULB as a corresponding test bed, and the
ULB flight envelope and agility allow faithful real time emulation of crucial final descent phase of lunar landers.

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Repeatability during and quick turn around between flights enable the fast exploration of trajectory trade space, and
the ability for piloted as well as autonomous operations allows the stepwise implementation of GN&C capabilities
and provides significant risk reduction during ‘closing the loop’ under pilot oversight.
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Figure 3. Main Trajectory Parameters for Lunar Lander Final Approach Example.
B. LADAR Data Collection
The objective of this experiment was to assess the performance characteristics of a LADAR 3D imaging system
on a flying platform, for example with respect to eventual capabilities for full darkness terrain and landing zone
mapping and hazard avoidance.
Boeing configured the test bed components of the so-called Capital Equipment LADAR for Testing Integrated
Capabilities (CELTIC) 3D Flash LADAR into a flight configuration and successfully flew a Spectrolab Geiger
mode Avalanche PhotoDiode (GmAPD) array on the ULB. The LADAR experiment used the following sensors and
components, which were collocated on a Sagebrush Model 20 gimbal mount that was attached upside down on the
ULB chin mount on the lower front fuselage at a 60 degree down look angle with a swath of about 10 degrees, as
shown in Figure 4:
• Photon counting BSVS custom 3D LADAR GmAPD array camera with 10 mradians Field of View and
single photon sensitivity
• Imperx Lynx COTS visible camera with 0.1 radians Field of View
• Keopsys Commercial Off The Shelf (COTS) Model KULT pulsed laser with 1.064 microns wavelength
On board equipment not integrated on the gimbal was installed in the ULB backseat instrumentation rack area.
Flights were performed at 300 m altitude and 2 kts ground speed. Targets of interest included slanted ground
planes, uneven terrain, camouflage netting, buildings and vehicles, persons, and railroad tracks The CELTIC used a
continuous scan mode for the gimbal, with triggers from the data acquisition computer. GPS data, gimbal position
angles and visible camera data were recorded at the fastest possible rate, and the 3D LADAR data were archived as
well. The LADAR collection portion of the scan was found to be not optimally aligned, and only half of the array
was receiving returns. It was however possible to still generate partial imagery as shown in Figure 5. The visible
imagery yielded a very smooth stabilized scan, as shown in Figure 6.
The experiment flight design and packaging was found to be excellent, and the integration onto the helicopter
went extremely well. The LADAR test was a major step forward in moving this system from a ground test bed
towards operational applications and demonstrating flight operations.

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Figure 4. Flash LADAR Installation.
Figure 5. LADAR Imagery Example.
Figure 6. Visible Imagery Example.

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C. Crater Navigation System
The crater navigation system is based on Boeing Orbital Express sensor and avionics technologies, which
provide a baseline to support the development of Guidance, Navigation and Control (GN&C) approaches and
capabilities for the next generation of lunar and planetary landers. The Orbital Express sensor suite and Vision-based
Software for Track, Attitude, and Ranging (Vis-STAR) with LADAR integration enables data fusion for safe
landing and autonomous rendezvous and proximity operations and reduces the associated risk for future programs.
Crater (topography feature-based) navigation utilizes the relative position of known landmarks to help determine the
navigation state of a spacecraft or lander both in orbit as well as during descent to a lunar or planetary surface. The
application of this process has first been demonstrated in simulations utilizing available lunar surface maps as well
as artificial planetary surfaces. The selected features for the initial development of this capability have been craters.
It is however anticipated that the technique will be readily adaptable to other surface features such as rilles, ridges,
and dry fluvial topographies, e.g. dry river beds, canyons, or washes.
The objective of this flight test was to collect real terrestrial digital imagery data of relevant topographical
features over terrain which simulates extraterrestrial bodies, utilizing well characterized spacecraft sensors.
Specifically, the collection of both visible and infrared sensor imagery of craters and other surface features under
varying geometric viewing and lighting conditions was performed in the course of several passes over desired
surface features for correlation to 6-Degree of Freedom (6-DOF) platform (truth) data for the development of
navigation algorithms for planetary and lunar orbital and landing missions.
The crater navigation sensor package comprised the Orbital Express engineering development unit Infrared (IR)
and visible cameras and redundant COTS IR and visible cameras with the following specifications:
• Vionics VISCAM2 with 40° Field of View
• Vionics IRC with 50 mm lens and 19° x 14° Field of View
• Sony SX900 with 8 mm lens and 42° Field of View (backup for VISCAM2)
• Vionics AIR 18° x 14° Field of View (backup for IRC)
The sensors were rigidly mounted with parallel axes of view on an aluminum plate. The four cameras had a fixed
focus and were set to fixed exposure. The sensor platform was attached to the ULB chin mount with the cameras
pointing straight down, and vibration isolation was added at installation. Raw image data were recorded on
redundant laptop computers, which were accommodated in a flight-worthy container.
Figure 7 shows the installation of the sensor platform.
Figure 7. Crater Navigation Sensor Platform Installation.
Three laptop computers were accommodated in the backseat instrumentation rack area for data recording to
provide redundancy in case of a camera or hard drive failure:

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• Laptop #1 recorded VISCAM and IRC images at 2 frames per second (fps) into raw image files (16
GBytes/hr)
• Laptop #2 recorded Sony at 2 fps into raw image file (15 GBytes/hr) and ULB GPS/INS data (RS232)
at 115 kbps into raw data file (4 MBytes/hr)
• Laptop #3 recorded AIR at 30 fps (16.6 GBytes/hr) into Audio/Video Interleaved (AVI) file
The laptops were mounted in a metal case with vibration isolation material and cooling provisions and were
operated in a closed display configuration when airborne. They were initialized via ground computer and Local Area
Network (LAN), and data recording was started prior to ULB engine on (disconnected prior to flight). The internal
arrangement of the data recording unit in the ULB backseat instrumentation rack area is shown in Figure 8.
Figure 8. Crater Navigation Recording Unit Accommodation.
Topographic features which mimic lunar respectively Martian terrain, such as wrinkled ridges, pits resembling
craters, alluvial fans and scarps around a central basin, were identified and selected in the vicinity of Winslow as
targets for image collection, and flight patterns were defined to allow the recording of imagery showing several of
the features of interest in a single flight while performing continuous data collection at multiple altitudes as well as
on descending trajectories. Test site imagery in the Winslow vicinity was successfully collected along the defined
flight path, and data from two 90 minute flights at low and moderate sun angles were obtained. Four sites with
distinctive Mars-like terrain features were surveyed at three altitudes and two rapid descent trajectories in each
flight.
Clear, high-quality imagery data were gathered on both flights from the two visible cameras, while the two IR
cameras collected data of varying quality throughout the flights due to integration time settings for the larger IR unit,
causing some image smear, and temperature variations on the smaller IR camera, causing some stability concerns
relative to its on-the-ground calibration settings. All cameras and data recording equipment performed however
without failure and according to design. Figure 9 shows a representative example of the visible imagery, and Figure
10 presents an example of the infrared imagery.
The Winslow test site imagery met expectations for similarity to Martian terrain and can be employed to develop
and test orbital and landing algorithms for planetary navigation. The ULB platform was found to be well suited for
obtaining extra-terrestrial-like image data in this setting, and the ULB data eliminate the need to rely solely on
simulations or high-altitude planetary survey images with limited resolution for development of planetary navigation
solutions. The imagery collected is being used to advance the state of algorithms to support low altitude orbit
determination/navigation and Precision Landing and Hazard Avoidance capabilities. Real imagery such as what has
been collected as part of this effort is vital in providing a way to verify that all features of interest are identifiable
under a variety of lighting and terrain conditions in order to validate and enhance algorithm capabilities.

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Figure 9. Visible Imagery Example.
Figure 10. Infrared Imagery Example.
D. Pseudolite Navigation System
Pseudolites ("pseudo-satellites") are typically small transceivers that are used in an array to create a local,
ground-based GPS alternative by emitting ranging signals. A Pseudolite landing and surface navigation system
allows a user to perform precision navigation relative to a Pseudolite array without the use of or reliance on GPS.
The goal of the Pseudolite landing and surface navigation system test was to demonstrate the ability to acquire
Pseudolite signals and compute a navigation solution during a simulated lunar lander descent. Specific objectives
were to demonstrate precision navigation without GPS, both for surface vehicle navigation as well as flight vehicle
navigation and landing, to evaluate the suitability of the open frequency band (915 MHz), to evaluate the prototype
receiver/Pseudolite hardware with respect to signal performance, near/far susceptibility, and navigation algorithms,
and to collect raw navigation signals for post-processing with Boeing navigation algorithms. The on board setup
flown during the test included a receiver, a receiver power supply with cables, a 915 MHz receiver antenna with
mount and SubMiniature version A (SMA) cable, and a laptop with RS-232 port for monitoring and configuration.
Receiver control and data collection was provided by a Center for Remote Sensing (CRS) supplied program running
on a Boeing-supplied computer. The on board computer program could be initialized before vehicle power-up and
run without user intervention. The on board hardware equipment was accommodated in the backseat instrumentation
rack area of the helicopter, while the receiver antenna was attached underneath the fuselage of the helicopter pointed
down and as far away as possible from other objects on the bottom of the helicopter to minimize impact on visibility
and interference. The integrated flight hardware is shown in Figure 11.

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Figure 11. Pseudolite On Board Installation.
The Pseudolite ground array consisted of four transmitters placed roughly one mile apart at the corners of a
square on airport property respectively in its vicinity surrounding a designated helicopter landing zone. All four
Pseudolites were placed at ground level on approximately level terrain. For this initial test campaign the Pseudolites
initialized themselves using GPS. The configuration of each Pseudolite ground station comprised a transmitter, a
power amplifier, a transmitter antenna, a GPS antenna, and a laptop for data monitoring and recording. The
Pseudolite transmitter produces a GPS-like signal on a 915 MHz carrier. The signal is supplied to the adjustable
power amplifier for transmission with a maximum of 1 W of power. The transmit antenna and the GPS antenna were
mounted on tripods. The Pseudolite transmitter and power amplifier run on 115 V AC, which was provided by a
portable 2 kW gas generator at each ground station location. The Pseudolite transmitter and power amplifier were
packaged in a rugged case for shipping and operation. An actual ground station installation is shown in Figure 12.
Figure 12. Pseudolite Ground Station Installation.

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Two flight tests were performed, which constitute the first known rotorcraft Pseudolite navigation test and
produced useful data, based on the successful acquisition of all four ground stations. These flights demonstrated
tracking during simulated lunar landings as well as conventional rotorcraft landings and vicinity operations at
distances of up to 8 miles. The basic ability to perform precision navigation with Pseudolite-only signals was
successfully demonstrated. The effects of multipath and signal strength on navigation performance were also
studied. Data collected during the tests consisted of:
• Raw measurements and timing information collected by the navigation receiver from the Pseudolites
• Computed vehicle position and velocity information
• Received Pseudolite power levels and receiver health information
• Position and velocity information from the vehicle’s GPS truth system for comparison to the system
under test
• Pseudolite performance and GPS self-survey information
Pseudolite-based airborne navigation was found to be viable and capable of aiding GPS for autonomous/piloted
landings, precision navigation in GPS-denied areas or other high-integrity operations as well as for extraterrestrial
navigation applications.
IV. Conclusion
The Boeing ULB MD-530-FF rotorcraft platform successfully performed flight test demonstrations of a variety
of lunar lander navigation related experiments in November 2007 in Winslow, AZ. The ULB helicopter was found
to be an extremely effective, versatile and agile test platform that can be rapidly adapted and reconfigured for
different missions within short turn around time even under austere conditions. The lean ULB program approach
with minimum overhead and short and direct communication paths allows the extremely responsive implementation
and execution of test efforts. Flight testing in Winslow was found to offer an effective, low cost environment with
minimum air traffic and electromagnetic interference despite the relatively Spartan infrastructure.
Close coordination and collaboration between individual experimenters and the ULB project was vital for the
success of the test efforts. All experiments were successfully executed within the planned six day window of
opportunity and yielded good to excellent results. Most experiments functioned completely or predominantly as
planned on the first attempt. Minor issues on some experiments yielded important insights into potential failure
sources and associated improvements for follow on activities and operational applications. The Pseudolite precision
navigation experiment experienced an initial malfunction due to thermal problems of on board equipment, but the
fault was identified and a solution approach was developed, implemented, ground tested and successfully reflown
during the ongoing campaign.
The ULB proved to be a highly effective sensor/system test bed, with ample weight capacity, internal volume,
electrical power, and internal and external equipment attachment locations to accommodate all planned experiments.
The ULB AFCS was easily enabled to provide extremely low speed steady state lateral translation (1 meter/sec at
flight altitude) over potential landing areas. This capability allowed the carefully controlled performance evaluation
of optics and Radio Frequency (RF) based sensor systems intended for lunar lander navigation. Experiments
requiring in-flight system intervention were easily accommodated, as were experiments that functioned in a fully
autonomous nature. The successful flight test campaign of the ULB in the various configurations tested proved its
adaptability and viability in a wide range of sensor and avionics related technology demonstrations, especially
taking its capability to fly fully autonomously, but with a safety pilot on board to monitor operations and intervene
in potentially risky situations, into account. The ULB can therefore serve as a low cost, low risk, proven, highly
adaptive platform for stepwise sensor testing and evaluation of GN&C approaches and algorithms as well as early
demonstrations and maturation of other lunar lander related technologies, and it allows to build confidence in
GN&C approaches before implementing them for example in rocket based vehicles. It closes the cost, risk,
capability and schedule gaps between laboratory experiments and custom built demonstrators or full scale
applications and could also be used to provide safe, responsive, cost effective astronaut training for NASA.