Miniaturization of Planetary
Atmospheric Probes
Tony Colaprete
NASA Ames
“Outline”
History of atmospheric entry probes and science
What probes have flown
What have they measured
What were their limitations
Building an entry probe
Survival First, Measure Later
Technological (and Physical) Limitations
Changing the paradigm
The curse of Galileo - Hand-me-down science
Enabling Sensors & Technology
Pico probes - New Architectures and Systems
Credits: Gary A. Allen, Jr., William H. Ailor, James O.
Arnold, Vinod B. Kapoor, Daniel J. Rasky, Ethiraj
Venkatapathy
History of planetary entry “probes”
Since the 1960’s:
Mercury,Gemini, Apollo, Soyuz , etc. (Earth)
PAET (Earth)
Pioneer Venus, Vega, Venera (Venus)
Viking, Pathfinder, MER, DS-2 (Mars)
Galileo (Jupiter)
Huygens (Titan)
Future (on the books):
Phoenix Lander (Mars)
Mars Science Laboratory (Mars)
ExoMars – ESA (Mars)
Talked about:
Venus SAGE
Titan Aerobot/Rover
Jupiter, Saturn & Neptune
Atmospheric Science: PAET, Pioneer-Venus,
Viking, Galileo and Huygens
PAET (1971), An Entry Probe
Experiment in the Earth’s Atmosphere
M = 62 kg, Minst = 14 Kg, Rb = .914 m
Viking (1976)
Pioneer-Venus (1978)
Galileo (1995 )
State-of-the-Art (16 years ago): Huygens
Probe specifics:
• 2.7 m diameter heat shield
• Total Probe mass of 349 kg
• 6 instruments (49 kg or 14%)
All In-Situ Mars Atmospheric Data…
In-Situ Mars Atmosphere Profiling
Viking 1 & 2:
• Atmospheric state variables during entry (direct).
• 5 minutes each
Pathfinder and MER:
• Atmospheric state variables during entry (derived).
• 5 minutes each
Phoenix:
• Atmospheric state variables during entry (derived).
• 5 minutes
In All, about 25 minutes has been spent making
measurements between the surface and 80 km.
And now for the rest of the data…
And now for the rest of the data…
Venus Profile
Titan Profile
clouds
z (km)
120
110
100
90
80
70
60
50
40
30
20
10
?
0
100 200 300 400 500 600 700 800
T (K)
In all, planetary entry probes have measured ~14 individual profiles
The limitations of entry science
• Up to this point it is very costly in terms of mass, and
always mass = $$
• Can only afford to fly a few (if your lucky) and
usually only one - Statistics of small numbers (e.g.,
Galileo)
• Limited lifetime – poor temporal coverage
The challenge is to change the way probes are done to
overcome these limitations!
Atmospheric Entry Mission & Probe Design
Probe mass fraction
Mission Design Considerations:
Payload
• Intended Science – Where are you headed?
• Key Factors: Mass, Volume, Power, Design
Complexities (risk) and Cost
• Science payload (mass, power, etc)
significantly impact both mission architecture
and hardware (mass, power, complexity and
cost) – Drives Probe Size
Range: 5%-25%
Aeroshell (TPS)
Range: 3% - 50%
Aeroshell (strcutures)
Range: 5% - 12%
Aeroshell Parachute
Range: 2% - 5%
Power/Thermal/Com
Range: 5% - 20%
Or bit Ins e r tion
(Propuls ion & Fue l)
Range: 15% - 40%
Entr y Pr obe
Range: 25% - 40%
Space cr aft/Bus / Com
Range: 25% - 40%
Spacecraft Mass fraction
Cassini Spacecraft Components
Huygen Mission Design
Galileo – A flight through a nuclear blast
About 50% of the probe was TPS
Designing for Hell
0.515
350
TPS mass fraction
entry
/Mass
TPS
Mass
• Calculations by Dr. G. Allen / M. Tauber,
ELORET based on Engineering Code by
Tauber, et. al.
0.505
250

0.500
200
0.495
150
0.490
100
Entry mass
• Carbon Phenolic TPS - TPS mass fraction
is insensitive to entry probe size
• Science mass available for microprobe
approx. 1 kg
Galileo:
Science Mass:
Base Radius:
Probe Mass: 338 kg,
8.3% of Entry Probe mass
1.28 m
2
• Galileo entry conditions 48 Km/sec, 6.64o E. angle, equatorial entry
0.485
50
0.480
0
0.2
0.3
0.4
0.5
R
0.6
/R
bas e
0.7
0.8
0.9
1
bas e (Galile o)
microprobe
The gas giants present extreme
performance limits to TPS
Entry mass (kg)
Jovian Entry TPS Study
300
Ballistic coefficient,  (kg/m )
0.510
Pascal – A Mars Network Mission Using
Micro Probes
Pascal Sample Network Configuration
Pascal – A Mars Network Mission
Pascal Probe Deployment Sequence
Pascal – A Mars Network Mission
Probe Entry System
Science Station
0.5 m
- 70° half angle cone
- Hemispherical backshell
- 20 kg entry mass
- RHU powered
Pascal Carrier S/C accommodates 24 Probes
with a Delta III or IV Launch Vehicle
ADCS and Telecom
Components
Spacecraft
Bus
Fixed Solar Array
Probe Dispenser
Panels (4)
Hydrazine Thrusters
Stowed in D3940 Fairing
MGA’s and LGA
Power and C&DH
Components
Pascal – A Mars Network Mission
Entry
•Speed = 6 km/s
•Landing in 4 minutes
Pascal EDL Sequence
Self
orientation
Aft dome
separates
Parachute
deployment separates
entry probe from
science package
Q = 700 Pa
M = 1.5 – 2.2
Airbag inflates
immediately after
chute deployment
Airbag protects
science station
at impact –
numerous
bounces
Chute separates after
first impact
Jettison
airbag and
initiate landed
operations
Pascal requires several enabling technologies/developments
Enabling Sensors - Venus SAGE
Atmospheric Structure Investigation
Provides information on all
atmospheric state variables, stability,
and winds during descent and landing.
Landing
Sphere
Wind
Temperature
Sensor Booms
Pressure
IMU &
Moutherboard
Accelerometers
Gyroscopes
Enabling Sensors - Amazing Shrinking Sensors
Cassini/Huygens ion source
The rmionic electron gun
GSFC developmental time of
flight mass spectrograph core
50 gm, 10 cm length
GSFC
2.54 cm
CNT based ion source
unde rgoing evaluation
Jamieson & P. Roman/ GS FC; L. Delizet,/ARC
GSFC Research thrust: one kg/one W
mass spectrograph with capability of
Cassini/Huygens technology 17 kg/ 15W
1/2 m m.
A miniaturized mass spectrometer
The Pico Reentry Probe (PREP)
Modular reentry probe:
• Conduct flight-testing of an
integrated entry system
• Flight qualification of subsystems
such as TPS, innovative sensors and
science instruments
• Perform low cost atmospheric
science experiments
Specifications:
• ~ 20 cm in diameter
• Total mass ~ 1 kg
• Payload mass ~ 0.3 kg
• Heatshield mass fraction < 7% (for
Mars entry)
Possible mission architectures
Multiple atmospheric sounders
• More valuable in atmospheres where remote sensing is difficult
(e.g., thick or opaque)
• …or for measurements that are difficult to make with remote
sensing (e.g., methane on Mars, water in Jupiter)
• “Ground” truth for remote sensing (e.g., winds, composition, state)
Landed Network
• Hard landers would retain the most simplicity
• Synoptic weather
• Seismic networks
• Penetrator (e.g., DS-2)
Crewed Descent
• Forward observers to high-value descent vehicles
Micro Probe System Considerations
Science instrument design
•Multiple integrated sensors
TPS
• Rethink design
• New materials for outer planets
Terminal descent & landing
• Parachute?
• Heat shield separation
• Novel Shapes?
Thermal and power management
• Extreme operational ranges
Data storage, processing, relay & comm.
• Miniature & ruggedized transmitters
Micro Probe System Considerations
Examples of integrated micro-systems
ST5 micro-sat
3corner micro-sat
Concluding Thought
“A personal impression is that more can and ought
to be done with simple sensors : a shift of
emphasis from exquisite construction to testing
and analysis.” – Ralph Lorenz
Existence Proof – NASA V-Team
NASA V-Team Descent Probe
• 4 accelerometers
• 3-axis gyro
• 2 external temperature
• 2 external pressure
• GPS
• Total mass ~3kg
The probe is no
longer a vehicle but
rather an instrument
into itself.