Miniaturization of Planetary Atmospheric Probes Tony Colaprete NASA Ames

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 “Outline” 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

Viking (1976) Galileo (1995 ) Pioneer-Venus (1978) PAET (1971), An Entry Probe Experiment in the Earth’s Atmosphere M = 62 kg, M inst = 14 Kg, R b =.914 m Atmospheric Science: PAET, Pioneer-Venus, Viking, Galileo and Huygens

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…

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-Situ Mars Atmosphere Profiling In All, about 25 minutes has been spent making measurements between the surface and 80 km.

And now for the rest of the data…

T (K) z (km) clouds ? Venus ProfileTitan Profile And now for the rest of the data… 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!

Huygen Mission Design Payload Range: 5%-25% Aeroshell (TPS) Range: 3% - 50% Aeroshell (strcutures) Range: 5% - 12% Aeroshell Parachute Range: 2% - 5% Power/Thermal/Com Range: 5% - 20% Spacecraft Mass fraction Probe mass fraction Cassini Spacecraft Components Atmospheric Entry Mission & Probe Design Mission Design Considerations: 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

Galileo – A flight through a nuclear blast About 50% of the probe was TPS

Jovian Entry TPS Study Calculations by Dr. G. Allen / M. Tauber, ELORET based on Engineering Code by Tauber, et. al. Galileo entry conditions 48 Km/sec, o E. angle, equatorial entry Carbon Phenolic TPS - TPS mass fraction is insensitive to entry probe size Science mass available for microprobe approx. 1 kg Galileo: Probe Mass: 338 kg, Science Mass: 8.3% of Entry Probe mass Base Radius: 1.28 m microprobe Designing for Hell The gas giants present extreme performance limits to TPS

Pascal Sample Network Configuration Pascal – A Mars Network Mission Using Micro Probes

Pascal Probe Deployment Sequence Pascal – A Mars Network Mission

Probe Entry System 0.5 m Science Station - 70° half angle cone - Hemispherical backshell - 20 kg entry mass - RHU powered Pascal – A Mars Network Mission

Pascal Carrier S/C accommodates 24 Probes with a Delta III or IV Launch Vehicle Stowed in D3940 Fairing Fixed Solar Array ADCS and Telecom Components Power and C&DH Components Hydrazine Thrusters MGA’s and LGA Spacecraft Bus Probe Dispenser Panels (4)

Pascal EDL Sequence Self orientation Aft dome separates Aft dome separates Parachute deployment separates entry probe from science package Q = 700 Pa M = 1.5 – 2.2 Parachute deployment separates entry probe from science package Q = 700 Pa M = 1.5 – 2.2 Jettison airbag and initiate landed operations Jettison airbag and initiate landed operations Airbag protects science station at impact – numerous bounces Airbag inflates immediately after chute deployment Entry Speed = 6 km/s Landing in 4 minutes Entry Speed = 6 km/s Landing in 4 minutes Chute separates after first impact Pascal – A Mars Network Mission Pascal requires several enabling technologies/developments

Landing Sphere Sensor Booms Wind Temperature Pressure Accelerometers Gyroscopes Enabling Sensors - Venus SAGE IMU & Moutherboard Provides information on all atmospheric state variables, stability, and winds during descent and landing. Atmospheric Structure Investigation

Enabling Sensors - Amazing Shrinking Sensors A miniaturized mass spectrometer

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) The Pico Reentry Probe (PREP)

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

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

3corner micro-sat ST5 micro-sat Examples of integrated micro-systems

“ 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 Lorentz Concluding Thought

NASA V-Team Descent Probe 4 accelerometers 3-axis gyro 2 external temperature 2 external pressure GPS Total mass ~3kg Existence Proof – NASA V-Team The probe is no longer a vehicle but rather an instrument into itself.