Planetary Science Summer School 2002

1
Planetary Science Summer School 2002

• Mars Atmospheric Boundary Layer Explorer
• (Mars ABLE)
• Scout Proposal Summary
• Study funded by NASA HQ Code S

2
Executive Summary

• Science Goal Boundary layer atmospherics
• Secondary goal Geomorphology
• Science Mission Length 2 weeks (extendable)
• System Tethered, zero pressure Balloon with
  entry system
• Class IVa
• Launch Vehicle Delta 2425
• Total Mass 506 kg
• Total cost 347 M

3
Mars ABLE

• Mars ABLE cruise stage and deployed configuration

4
Agenda

• Science Objectives
• Instrumentation
• Atmosphere
• Imaging and Geomorphology
• Spacecraft Configuration
• Subsystem Description
• Program Management
• Mass, schedule, budget, risk

5
Primary Scientific Objectives

• Atmospheric polar boundary layer
• First direct wind, temperature, pressure and
  water vapor profile measurements (0 m -500 m)
  to characterize the diurnal cycle of the Mars
  polar boundary layer in early summer
• Two week proof of concept for multiple tethered
  balloon mission investigations of boundary layer
  variability and surface-atmosphere interactions
• Bridge the gap between surface and orbiter
  measurements

6
Secondary Scientific Objectives

• Imaging and geomorphology
• First aerial photographs that provide a link
  between surface and orbital imagery
• Ultra-high resolution imaging of polar
  geomorphology
• Surface environment
• First characterization of the oxidizing potential
  of the polar surface environment with miniature
  sensor technology
• Atmospheric oxidants
• H2O2, O3, H2O, etc.
• First measurements of static and low frequency
  electric fields near the surface of Mars

7
Landing Site

• 80 5 North Polar Layered Terrain

• Final site selection to be determined six months
  prior to launch
• Community landing site workshops

MOC E03-00889 courtesy of MSSS
8
Science

• MEPAG Goal Current climate
• Local cap edge diurnal circulation interaction
  between local thermal/katabatic flows and general
  circulation thought responsible for dust storm
  seeding (Kahn, 1992)
• Volatile defrosting regime (MOC imagery)
• MEPAG Goal Follow the water
• Complement MRO 2005 PMIRR H2O global coverage
  with near surface (z, t) distribution in key H2O
  source region

9
Current Climate

• Orbiter measurements uncertain in near surface lt2
  km region
• Surface lander measurements at 2 m
• Region 2 m - 500 m governs air-surface
  interactions

10
Volatile Defrosting Regime

• Curious MOC images suggest local thermal
  circulations and wind influence defrosting
  patterns
• Dark defrosting(?) features
• Arrow structure

MGS MOC Images courtesy of MSSS
11
Science

• MEPAG Goal Dust, surface interactions and human
  exploration
• Surface friction velocity (U), key unknown in
  Mars GCMS (Hollingworth, 2001)
• Related to dust lifting capability empirically
• U 2-3ms-1 for sand grains 200-500um (Polkko et
  al, 2000)
• 5ms-1 for dust 1um
• Oxidation and ELF measurements to characterize
  surface environment for human exploration
• MEPAG Goal Past climate
• Geomorphology of polar layered deposits and
  seasonal frost cover

12
Meteorology Measurements

• Tethered balloon
• Two week mission to characterize polar spring
  diurnal cycle
• Anchoring for boundary layer temperature,
  pressure, and wind profile measurements
• Vertical spatial sampling at (0,) 2, 10, 100,
  200, 500 m
• Temporal sampling at 1 Hz (turbulence fluxes)
• Integrated instrument package with Pathfinder
  ASI/MET heritage
• Additional new wind and water vapor sensors,
  transmitter, battery
• Data analysis
• Height registration from modeling of tether
  catenary using P, U, T 500m data and imager data

13
Meteorology Instrument Package

• Measurements
• Pressure
• TAVIS magnetic reluctance diaphragm sensor
• (VIKING, PATHFINDER,-0.01mbar)
• Temperature
• Thin-wire thermocouple (PATHFINDER, -0.1K)
• Horizontal wind speeds
• Hot film anemometer (BEAGLE II, 0-60ms-1,
  -0.5ms-1)
• Water vapor
• Miniature laser diode spectrometer (JPL
  development, TRL 6)
• Utilizes Heritage Technology

14
Mars Atmospheric Oxidant Sensor

• Will quantify and characterize the possible
  species of oxidants in the Martian atmosphere
• Can reveal the role oxidants have played in the
  evolution of Martian chemistry
• Important in development of missions for the
  future human habitation of Mars

PI Aaron Zent, NASA Ames
15
Extremely Low Frequency (ELF) Sensor

• Measures Mars fair weather field (due to
  radioisotopes, cosmic rays, etc.)
• Measures the induced electric field due to dust
  devil activity
• Horizontal plate antenna placed low on the tether
  and near the surface

16
Static Field Sensors

• A cold, dry Martian climate is conducive to
  electrostatic charging of the airborne dust
  (triboelectric effect)
• Uses MECA technology to measure the residual
  Electric Field on Mars

17
Narrow Angle Imager

• Requirements
• Daylight imaging
• Panchromatic visible (400 1000 nm)
• 2 cm GSD (ground sample distance) from 500 m
• 3 cm resolution from 500 m
• 40 m x 40 m image size
• 168 images (mission total)
• Specifications
• 2048 x 2048 pixels 9 ?m x 9 ?m
• 10-bit digitization
• 225 mm focal length lens
• 1 ms exposure, frame transfer

18
Context Images

• MRO CTX 30 km swath _at_ 6 m resolution to locate
  actual landing site
• MRO HiRISE 1230 x1230 m _at_ 30 cm resolution
  context image
• Descent images?

19
Context Images
MRO CTX image to locate actual landing - 30 km
swath
MRO HiRISE context image 1.2 x 1.2 km
Landing ellipse - 10 x 100 km
20
Imager Operations

• No navigation ? random image locations
• Image selection options
• Preview and select
• On-board prioritization

21
Preview and Select

• Each sol downlink 40 preview images compressed
  40x and 12 selected images (from previous sol)
  compressed 8X

22
On-board Prioritization

• Acquire gt 14 images/sol
• On-board computer catalogs locations of previous
  images referenced to context image
• Priority function
• Seek overlap for temporal coverage at selected
  location
• Avoid overlap for maximum spatial coverage
• Downlink top 14 images each sol

23
Spatial Coverage
MRO HiRISE context image 1230 x 1230 m
168 images 269,000 m2 (137 coverage)
MER Pancam 2 cm pixels to 70 m radius 15,400 m2
250 m radius from anchor 196,000 m2
40 m x 40 m image 133 x 133 HiRISE pixels
1600 m2
24
Requirements Flowdown

• 2048 x 2048 x 10-bits, compressed 8X ? 5.25
  Mb/image
• 168 images 560 previews ? 100 Mb/day for 14
  days
• lt 1 cm motion blur ?
• lt 10 m/s lateral motion
• lt 1/s pitch/roll, 25/s yaw

25
Instrumentation Summary
Mass includes 30 contingency
26
Instrument Mass/Power Budget

• Magnetometer 30 g (1 ea), 150 mW
• ELF - 100 g (1 ea), 300 mW
• Static field sensor 20 g (5 ea), 100 mW
• MET pkg 100 g (5 ea), 800 mW
• MAOS 55 g, 250 mW
• Point spec, 300 g (1 ea), 100 mW

27
Mars ABLE Spacecraft

• Carrier System
• Spacecraft bus
• Propulsion system
• Entry System
• Inflation system
• Heat shield
• Free-float system
• Balloon
• Gondola
• Instruments and Tether

MARS ABLE
500m
28
Carrier and Entry Vehicles

• Carrier
• Star scanner and sun sensors
• Passive thermal protection
• MLI
• 4 solar arrays on deployed booms with locking
  latch mechanism
• Entry Vehicle
• Inflation system
• 4 helium tanks
• Heat shield
• Tanks used as anchors after balloon inflation

29
Free-float system

• Balloon 20 m diameter, 0.5 mil thick,
  non-aluminized Mylar / polyethylene
• Tether 1 mm diameter, polyethylene
• Aluminum gondola
• solar array on deployed booms with locking latch
  mechanism

30
Carrier Power
Solar Array 4 x 1m2 , TJ, GaAs Primary
Battery 2 x 8 cell Li-SOCL2 16
AHr Electronics 11 x 6U Smart Solid
State Boards, COTS conversion
tech.
31
Entry Power
Thermal Battery 2 x 2AHr Electronics 6 x 6U
Smart Solid State Boards,
COTS conversion tech.
32
Balloon Gondola Power
Solar Array 1 x 0.26m2 , TJ,
GaAs Primary Battery 1 x 8 cell Li-Ion 5
Ahr Electronics 5 x 6U Smart Solid
State Boards, COTS
conversion tech.
33
Attitude and Control Cruise Stage

• Requirements
• Pointing control of geometric spin axis within 2
  degrees (7200 arcsec), 3 sigma
• Pointing knowledge of the geometric spin axis
  within 1 degree (3600 arcsec), 3 sigma
• Implementation
• Active spin-stabilized carrier
• Mechanically redundant thrusters
• Orient spin axis
• Control nutation
• Control spin rate
• Star scanner, sun sensor, IMU
• Determine stellar inertial attitude
• Estimate angular axis

34
Balloon Attitude and Control

• Knowledge of balloon azimuth angle to within a
  few degrees (3 sigma)
• Set of 10 coarse sun sensors (on gondola)

35
Attitude and Control Entry System

• Support release of parachute at required dynamic
  pressure
• Accelerometers for deceleration profile
• Internally redundant power conditioning
  electronics

36
Uplink Communications

• Communications facilitated via the DSN through
  orbiting assets
• 100 Mb per day
• 14 pictures per day _at_ 5.25 Mb per picture
• 27 Mb per day total for all other instruments
• 3 uplinks per day for 5 minutes each
• 1 photo sequencing command for downlink

37
Command and Data Handling

• R6000 processor
• 8051 controller
• 64 MB proc RAM for CDS/database
• 64 MB proc RAM for data storage
• Heritage system components
• 2 flight units

38
Mass Estimate
39
Program Schedule
40
Cost Estimate
41
Risk Management

• Most systems low risk due to flight heritage
• Balloon deployment and inflation development
  planned
• Some risk associated with instrumented tether
• Possible shock to tether and/or gondola due to
  impact
• Analysis to be completed
• TRL 7 or above

42
Alternate Designs Considered

• Multiple balloons for multiple locations
• Drifting balloons for imaging and spectrometry
  mission
• Montgolfiere balloon
• Mobile lander with pop-up balloon
• System anchored followed by break- away tether

43
Acknowledgements

• PSSS Anita Sohus, Coco Karipinski, Jason
  Adringa, Jean Clough, Kay Ferrari, Susan
  Braunheim
• Outside Consultants Jay Wu, Viktor Kerzhanovich
• Team I Bob Wilson , et. al
• Team X Bob Oberto, et. al.
• Thanks to all other JPL personnel who provided
  resources, time and inspiration