Transcript XSS-11 Targeting Concept

The ARES Mission to Mars:
The First Flight of an Airplane on Another Planet
Presented at the Aerospace Control and Guidance Systems Committee Meeting
October 21, 2005
By Jeff Zinchuk and Lee Norris
Draper Laboratory - Cambridge, MA
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Topics
• Background and Program Overview
– Science
– Airplane deployment and ground track
• LaRC Planetary Airplane Risk Reduction Activities
• Draper Guidance and Navigation Algorithm Activities
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ARES Mars Proposal Complements and
Extends the Core Mars Program
– Exploration of Mars requires gathering scientific and engineering data over large areas of the planet
– Airplanes enable exploration of areas inaccessible to rovers with increased resolution over orbiters; blends
ground truth of rovers with global measurements of orbiters
– Simultaneous in-situ measurements of Mars atmosphere, surface, and interior
– Science themes:
Crustal Magnetic anomalies (“where do we come from?”)
Regional atmospheric chemistry (“follow the water”)
to determine climate history and ability to support3past life
* Planetary airplanes are a new platform for planetary science and exploration
Science Themes
Crustal Magnetism
Builds on Viking, Mars Global Surveyor,
and Odyssey discoveries, providing a
window into the evolution of Mars
atmosphere, surface, and interior
–
–
ARES extends MGS-discovered crustal
magnetic data to high spatial resolution
to understand its nature and origin
An aeromagnetic survey is utilized to
characterize the crustal magnetism
source structure
Near Surface Atmospheric
Chemistry
–
–
“Follow the water,” chemically-active
gases and precise isotopic
measurements
Potential gases of biogenic & volcanic
origin and atmospheric state variables
Underlying Geology & Mineralogy
–
–
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Geologic understanding of the oldest
known crust in the solar system
Understanding mineralogy associated
with the crustal magnetic anomalies
Reference Science Payload
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Straightforward Mission Architecture Maximizes
Use of Proven Technologies and Existing Infrastructure
– Short duration, scripted mission minimizes operations complexity
– Traverse and measurement techniques similar to those employed on earth
– Heritage carrier spacecraft (Genesis/Odyssey) and Entry System (MPF/MER)
Launch: Oct-Nov 2011
Flight: August 2012
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Airplane Deployment
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ARES Flight on Mars – Entry Video
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Pre-Planned Controlled Scientific Survey
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Flight Path and Navigation Requirements
Head North
Science
Race Track
Science
302.9 km
357.1 km (42.5
min)
28.3 km
36.0 min
3.4 min
5 km
100 km
100 km
100 km
11.9 min
11.9 min
11.9 min
14.1 km
14.1 km
1.7 min
1.7 min
5 km
800 km total
95.2 min
0.6 min
140 km
16.7 min
Approach
to Race
Track
Science
180° W, 45-50° S
N
W
E
S
Not to
scale!
Avg ground speed 140 m/s
Min turning radius 9 km
Avg terrain height 1.5 km
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ARES Flight on Mars – Traverse Video
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ARES Status
•
Draper supported NASA’s Langley Research Center in 2002-3 for a
Mars Scout Program Phase A Study “Aerial Regional-Scale
Environmental Survey” (ARES) of Mars
– Scout Program run on 4-year cycles; complements Mars Exploration Program
– ARES one of four proposals (25 submitted) selected for Phase A studies
•
ARES not selected for implementation (Phases B, C, D) but LaRC
will re-propose in ’06
– Phoenix selected; perceived to be low risk
– ARES science was rated Category 1
– Some perceived technology development risks (cost/schedule)
•
ARES Team
–
–
–
–
–
JPL - Program management, mission design and operations
LaRC - Atmospheric science and aeronautic
Lockheed - Heritage Genesis-design S/C
Aurora - Airframe subsystems
Draper - Autonomous GN&C and sensors, integrated avionics subsystem
(computer/flight software, hardware-in-the-loop simulation (HILSim)
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ARES transitions into PARR
•
During Phase A study, a high altitude drop demonstration (HADD-1)
was performed using half-scale model of airplane
•
Although ARES established viability of airplane-based planetary
exploration, implementation risk must be lowered to enable mission
selection in ’07
– PARR program objective is to reduce risk in high risk technology areas
•
Program risk reduction strategy
– Use ARES design reference mission and entry system hardware as
baseline designs
– Demonstrate perceived high risk technology in ground-based tests
(HILSim and propulsion components)
– Show “system-level” readiness via additional HADDs (2, 3…)
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PARR Program - Technology Focus
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FCS Risk Reduction Tasks for GNC
– Develop 6 DOF simulation using airplane performance and
environmental models to support analysis and performance
characterization of potential GN&C implementations for an
airplane flight on Mars
•
•
•
•
•
•
Assess GN&C sensor suites
Assess trajectories
Assess guidance algorithms
Assess navigation algorithms
Develop large Kalman filter for navigation options
Develop guidance algorithms for two types of mission; straight
or parallel paths
• Incorporate LaRC-supplied control algorithms
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Draper Items to Consider
• How to improve initial state
knowledge (or accommodate
large velocity uncertainty)
• How to accommodate significant
uncertainty in winds
• Strategies for altitude
determination
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PARR Guidance, Navigation, And Control
• ADS Data
• Radar Altimeter Data
• IMU Data
• Initial Condition Data
• Other Sensor Data
Navigation
• Mission Data
• Nominal Trajectory
• Position
• Velocity
• Heading Cmd
• Altitude Cmd
Guidance
• Attitude
• Body Rates
• ADS Data
Control
• Aileron Cmd
• Rudder Cmd
• Elevator Cmd
• Engine Cmd
Navigation – determines the position/velocity/attitude state of the aircraft at the
current time
Guidance – determines the heading and altitude commands necessary to fly the
desired path
Control – determines the lifting surface and engine commands needed to meet
Guidance commands
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Aircraft Model And Control System
•
Aircraft model and Control
algorithms provided by NASA
Langley
Control System Characteristics
Step Response
•
Preliminary versions currently in
use in Draper 6DOF simulation
q
•
90 deg
60 deg
Preliminary Navigation and
Guidance algorithms are being
designed based on this simulation
30 deg
t
•
Primary interfaces to Control are
heading command and altitude
command
•
Heading rate command capability
may be added at a later date
q dot
Angular Rate
90 deg
60
30
t
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PARR Navigation
Baseline Instrumentation
Requirements
Inertial Measurement Unit (IMU) 
delta velocity, delta angle
• Determine near optimal estimate of
current position, velocity, and attitude
state of the aircraft for Guidance by
blending available sensor data
Radar Altimeter
• Estimate the aircraft attitude states
needed by Control
Air Data System (ADS)
• Angle Of Attack
• Angle Of Sideslip
• Airspeed
• Barometric Altitude
• Estimate the three components of wind
velocity for use by Guidance in
implementing the trajectory
Optional Instrumentation
• Locate previous path points (see
below) which can be used in Guidance
in implementing a “parallel ground path”
trajectory
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• Camera (Optical Flow)
• Sun Sensor
• Laser Altimeter
• Etc.
PARR Navigation Filter
Filter Design
State Vector
• The Navigation filter blends
information from a variety of sensors
to form the best estimate of the
current state of the aircraft
Rac
position (3 elements)
Vac
velocity (3 elements)
qac
attitude (3 elements)
Ab
• The relative weightings of the sensor
measurements are based on the
(statistically expressed) expected
qualities of the measurements
Asfe
accelerometer errors (9 elements)
Amar
Gb
• A Kalman filter provides the minimum
variance linear estimate of the state
of the aircraft assuming Gaussian
measurement error from the sensors
Gsfe
gyro errors (9 elements)
Gmar
GR
• The Kalman filter estimates not only
the aircraft state but also system
errors which affect the aircraft state
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gravity model error (3 elements)
Wned
wind speed (3 elements)
PPP
previous path points (12 elements)
Previous Path Points
1.)
2
5
1
4
3.)
• The desired trajectory is
nominally oriented with
legs 1, 3, and 5 aligned
with North
3 • Legs 1, 3, and 5 should be
parallel
• Legs 1, 3, and 5 are 100
km in length
• Legs 2 and 4 are less than
5 km in length
• Navigation will estimate the
location of four points along
the first leg
• In addition to estimating the
current state of the aircraft,
Navigation will continue to
estimate the location of
these four previous points
throughout the mission
• This allows updating of the
estimates when the wind
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values are better known
2.)
1
• The turns between legs
provide observability of
the wind
• Wind estimates on the
first leg will not be precise
• As a result, leg 1 may be
curved due to unknown
wind
4.)
• The previous path
points will be used
by Guidance to
construct legs 3 and
5 parallel to leg 1
Navigation Results
•
•
Relative Navigation error is better than absolute Navigation error
Preliminary covariance analysis indicates relative error of 3 km 1 sigma
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PARR Guidance
Issues
Requirements
• Provide heading commands to
implement an open loop (non-parallel
path) trajectory
• The primary issue for Guidance is
dealing with the effect of uncertain
winds on the groundtrack of the
aircraft
• Provide heading commands to
implement a parallel ground path
trajectory
• The Mars atmosphere is
unpredictable and unmodeled
• Compensate for the effects of winds
along the path for all trajectories
• Navigation can accurately estimate a
constant wind
• Provide altitude commands to
implement the desired altitude profile
• The issue is not the speed or direction
of the wind, but the degree of
variability
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• If the components of the wind change
significantly with time or distance,
Guidance will find it more difficult to
accurately hold the desired
groundtrack
Lateral Channel Guidance
• The trajectory will be defined by a
series of points along the desired path
• These points may be adjusted during
the flight to shape the second and third
legs to match the shape of the first
desired
heading
• Guidance will develop heading
commands to lead the aircraft onto the
desired trajectory
d
• The heading commands will “look
ahead” along the trajectory to anticipate
turns
heading command =
desired heading +
f(d) +
f(rate of change of desired heading)
• The commanded heading will be
adjusted to null the estimated wind so
that the desired groundtrack is
maintained
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Vertical Channel Guidance
Constant Altitude
• Three (or more) options exist for the altitude
channel as indicated
• The requirements for the gravimeter are
believed to be “constant altitude” above the
ellipsoid
Terrain Following
• The terrain following approach is most easily
implemented using the radar altimeter
• The altitude requirements for other science
missions are not yet specified
Modified Constant Altitude
• The baseline approach for altitude is modified
constant altitude, in which the aircraft flies at a
constant altitude unless the distance to the local
terrain (as measured by the radar altimeter)
goes below a threshold, in which case the
aircraft will climb to maintain the threshold
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Guidance Results (Without Wind)
• Plot shows a test trajectory
used in evaluating
Guidance algorithms
• Trajectory is the basic
shape of the proposed
groundtrack for
magnetometer studies
• Tracking error is least
during straight legs
• Improved performance is
expected as further
Guidance development
occurs
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Guidance And Navigation Trade Studies
Alternate Sensors
Purpose
• At this point the science which drives the mission
has not been firmly specified
• Several alternative combinations of instruments
and trajectories will be evaluated such that when
the science requirements are specified, a
significant portion of the required design will have
been done
• The goal is to provide a “catalog” of options which
specify the instrumentation and trajectories
necessary to meet a variety of objectives
• The baseline set of sensors have been
evaluated using preliminary covariance analysis
and appears to be satisfactory for a variety of
missions
• Alternate sensors such as a camera with image
processing may be required if the trajectory
must pass over a specific landmark
• Additional sensors may also be required for
increased accuracy or redundancy
Modified Trajectories
Alternate Trajectories
• Several non-parallel path trajectories will be
assessed (maximum distance North, dogleg,
etc.) to support atmospheric science
missions
• At least one parallel path trajectory will be
assessed to support magnetic field studies
• New trajectories may arise due to as yet
unspecified science requirements
• Wind speed and direction are most
observable when measurements are made
in two orthogonal directions
• This implies that wind estimates are
generally not accurate until the second leg of
a parallel path trajectory
• Wind knowledge can be obtained earlier by
doing a series of maneuvers prior to initiating
leg 1
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Program Status
•
Draper has 6 DOF deterministic simulation up and running
– Based on LaRC aerodynamic database and initial control laws
– Guidance and navigation algorithms are being integrated to assess
navigation performance under various trajectories and sensor suites
– Airplane control laws are still being developed at LaRC to incorporate
additional control modes for robust deployment and pull out
– Focus will be on analyzing absolute and relative navigation performance
– 6 month analysis to support science selection and proposal underway
•
EM model of flight hardware has been procured and is running with first
flight software build
– GNC code will be embedded in RAD750 flight processor and fly Hardwarein-the-Loop 6 DOF simulation
– Processor will be executing airplane flight control, and science data
collection, compression, and telemetry
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