Neptune: the gateway to the Kuiper Belt Innovative Mission Concept Argo for New Frontiers 04 • Fly by a Trojan (no Jupiter GA) or Jupiter • Gravity assist from Saturn Voyage Through the • Fly by Neptune/Triton system Outer Solar System • Fly by a scientifically-selected Kuiper Belt Object
Key Characteristics Candice Hansen (JPL) • Focused science mission Heidi B. Hammel (Space Science Institute) • Simple mission profile • Current instrument technology (NH) with Don Banfield (Cornell), Amanda Hendrix (JPL), Krishan Khurana (UCLA), Damon Landau (JPL), • Current spacecraft technology (NH) Alfred McEwen (U. Arizona), Linda Spilker (JPL), • Capable payload Tom Spilker (JPL), John Stansberry (U. Arizona), Ed Stone (Caltech) , Nathan Strange (JPL) • Radioisotope power
Argo and Decadal Priorities Argo and Decadal Priorities
NOSSE Report: "Opening New Frontiers in Space: Choices for the Next New Frontiers Announcement of Opportunity" • Planetary Decadal Survey also explicitly mentions In order for the New Frontiers Program to remain healthy over the long run, Neptune/Triton in multiple chapters it must maintain an influx of new ideas and grow the applicant pool for new missions. – Giant Planets, Large Satellites, Primitive Bodies Selected New A. Kuiper Belt – Pluto Explorer Innovative Mission Concepts • Neptune in far future because Flagship-class orbiter assumed B. Jupiter! Polar Orbiter with Probes • mission options outside the 3 remaining and 5 additional medium-sized! decadal 1975 1985 1995 2005 Three Remaining missions 1. South Pole-Aitkin Basin Sample Return Voyager 1 Cassini Pioneer 11 2. Venus In Situ Explorer • spurred by major scientific and Voyager 2 Orbiter technological developments made since 3. Comet Surface Sample Return the decadal survey! Five Additional • offer potential to dramatically advance fundamental scientific goals of the 4. Mars Network Science Pioneer 10 Voyager 1 Galileo New ! Cassini 5. Trojan/Centaur Reconnaissance decadal survey Pioneer 11Voyager 2 Orbiter Horizons 6. Asteroid! Rover/Sample Return • accomplish scientific investigations well 7. Io Observer beyond! the scope of the Discovery 8. Ganymede Observer != Argo program Argo Neptune Flyby is Crucial Access to Kuiper Belt Objects Argo’s accessible KB volume is ~4000x that of New Horizons The Neptune flyby enables the opportunity to: New Horizons cone of accessibility, without propulsive assistance, visit a Trojan Kuiper Belt Objects would be 1/4 the diameter of the period at the end of this swing past Saturn sentence.
fly by Neptune/Triton New Horizons, ~0.9° with propulsive assistance AND continue on to a KBO Carolyn Collins Petersen, and Richard Wright for Gemini Observatory Argo without Potentially in the Argo cone: propulsive assistance ~60° The Neptune flyby also 18 Cold Classical KBOs permits selection of the 40 KBOs with 200 < D < 400 km Neptune-to-KBO flight times 9 KBOs with D > 400 km (large KBOS) Neptune are ~1.5-3 years KBO with highest scientific interest Graphic created by Mark Petersen, several binary KBOs (KBO at 35-39 AU)
Compelling Neptune science Argo Science Opportunities
• Planetary System Architecture Fundamental New Science – Exoplanet population increasing – Comparative planetology of multiple KBOs: Pluto (large in situ), NH's KBO, dramatically Argo's Triton (captured), Argo's KBO (scientifically-selected) • Growing number of – First surface geology of a Trojan ice-giant-mass objects – First detailed images of Neptune's atmosphere in a new season • Pushing towards U/N equivalent – First detailed images of Triton's atmosphere after significant change distances in near future – First measurement of stability of an offset/tilted magnetic field – Microlensing – Near-IR radial velocity – First detailed images of Neptune's ring system in new dynamical state – Knowledge of local ice giants Incremental Science Engages a significant fraction of extremely limited – Ice giant interior measurements the planetary community • Earth-based efforts extraordinarily challenging compared to J & S – Small satellite science – Ice giants smaller – Ice giants much more distant Significant small icy body science as per decadal objectives – Ice giants colder Adapted from the ExoPlanet Task Force Presentation to the AAS, Austin, TX (Jan 2008) Progress on decadal Neptune science objectives – No currently planned mission to Neptune until an orbiter >2045 Sets the stage for a future Neptune System Flagship Orbiter Argo will set the stage for a future orbiter Achievable within New Frontiers resources Why New Frontiers 04? Argo Launch Windows for Fast Flights
• Preliminary • Launch options between 2017 and 2020 – Such windows occur every 12 years due to giant-planet gravity assist • Searched 2013-2027
• Two criteria • Neptune flagship orbiter precludes a KBO flyby (and likely no Trojan) V! <17 km/sec at Neptune arrival Time of Flight <10 yrs • Fills in the >50-year observational gap of a dynamic system – Will enable linking of future flagship to past flyby Both criteria met – The season has already changed on Neptune (solstice was 2005) Criteria not met – Loss of expertise from Voyager-era scientists from the 1989 Neptune flyby FF launch window ~2 yrs long The next window opens in 2027 • Exoplanetary Neptunes are now known to exist
– Knowledge of local ice giants is substantially less than gas giants Mission Trip Time V! (km/sec) Argo w/ JGA 8-10 yrs 12 - 16 Voyager 12 yrs 17 New Horizons 9.5 yrs 14
Outer Solar System Exploration: Current Plan Sample Trojan-Triton-KBO trajectories 2005 2015 2025 2035 New Horizons
Neptune Flagship?
Cassini Orbiter
A531/Bi-prop = 755 kg (delivered mass at KBO) A531/Bi-prop = 720 kg (delivered mass at KBO) Trojan: 2001 TW148, D ~ 20 km Trojan: Deikoon, D ~ 50 km Juno OP Triton: flyby alt 500 km at V = 13 km/s Trojan/Centaur Flyby? ! Triton: flyby alt 735 km at V! = 13 km/s Orbiter Flagship KBO: 2001 QX297, D ~ 150–350 km KBO: 2005 TB190, D ~ 250–600 km Cold Classical Large KBO
Trojan trajectories increase flight time, e.g., from 10 yrs to 13+ yrs Outer Solar System Exploration with Argo
2005 2015 2025 2035 New Horizons KBO Flyby 2038
Neptune/Triton Neptune Flyby 2032 Flagship? BACK UP CHARTS Argo NF04 Cassini Orbiter Saturn Flyby 2024
Juno OP Trojan Flyby 2023 Orbiter Flagship or !!!!!Jupiter Flyby 2023
Argo dates notional - still under study
Of $1B Boxes and Bricks Argo Mission Concept Team
“I heard that a joint NASA study by JPL and APL said NASA couldn’t send any mission to the outer Solar System for less than $1B.” This is wrong. • Principal Investigator (PI): Candice Hansen, Triton science The “Titan and Enceladus $1B Mission Feasibility Study” actually said: Pg 1-1: “no missions to Titan or Enceladus that achieve at least a moderate understanding • Deputy PI: Heidi Hammel, Neptune science beyond Cassini-Huygens were found to fit within the cost cap of 1 billion dollars (FY’06).” Relevance to Neptune: None • Project Scientist: Linda Spilker, ring science • Senior Science Advisor: Ed Stone “But I also heard that the study said NASA couldn’t even send a BRICK • Co-Investigator: John Stansberry, KBO science (spacecraft with no instruments) to the outer Solar System for less than $800M.” This is only partially correct. • Co-Investigator: Krishan Khurana, magnetospheric science CORRECT Pg 1-11: “Even the lowest cost mission studied [Enceladus flyby], without the cost of science payload, has a minimum expected cost of ~$800M.” • Mission Architect: Tom Spilker HOWEVER Pg 2-4: “[The Enceladus flyby’s] design (and therefore cost) was uniquely derived using actual cost data from the NH mission.” • Trajectory Design: Nathan Strange Neptune cost mitigators: Can use an Atlas 541 instead of a 551. Do not require Star-48 upper stage. Other savings under study. • Instrument Leads: Alfred McEwen, Don Banfield, Amanda Result: $$ available for Argo science payload within $800M cap Hendrix Past, Present, and Future of Outer Solar System Exploration Argo Science Objectives 1975 1985 1995 2005 2015 2025 2035 New Horizons Nearly all aspects of the Neptune system detectable from Earth have changed significantly since Voyager fly-by in 1989 Voyager 2 • Neptune's atmosphere shows fundamental differences in large- Voyager 2 scale structure – No Vgr GDS, significant atmospheric evolution on <5-yr timescale; evidence Voyager 1 Cassini for stratospheric heating since Voyager Pioneer 11 Voyager 2 Orbiter Neptune Measurement Goals – Small-scale cloud distribution – Atmospheric lightning – Magnetic field measurements in completely different Pioneer 10 Voyager 1 Galileo New Juno orientation Pioneer 11Voyager 2 Cassini OPF Orbiter Horizons Orbiter – First detailed compositional/spectral map – First detailed infrared map – Gravitational moments refined for interior models
Argo Science Objectives Argo Science Objectives - Triton
Nearly all aspects of the Neptune system detectable from Earth Map regions of Triton seen only from a distance by Voyager ("terra have changed significantly since Voyager fly-by in 1989 obscura") -- as well as more of Triton's northern hemisphere -- in order to extend the post-capture cratering history and reveal surface modification. Ring system science objectives (plus small satellites) • More of Triton's northern hemisphere will be sunlit – Most of it was in seasonal darkness for Voyager • The ring system has changed Terminator in 2027 Terra incognita – Arcs evolved within <8 yrs timeframe: 60°
Terminator in 1989 VGR era: 45° • Neptune’s Magnetosphere – Very complex and Terra Terra undetectable from Earth obscura obscura Argo Science Objectives - Triton Science Motivation
Argo will map the distribution of ices on Triton’s surface and • Relevance to life and habitability measure the atmospheric pressure to capture another point in time – "The giant planet story is the story of the Solar System." * for modelling climate change on an icy body • Direct implications for habitability • Delivery of volatiles to inner solar system
• Triton's atmosphere has changed Uranus significantly since the Voyager flyby in 1989 Neptune – Nitrogen and methane ices move — Argo can search for Saturn Jupiter seasonally from hemisphere to organic compounds hemisphere, causing the pressure of on Triton's active the atmosphere to vary with seasonal surface
Measurement Objectives
• Geologic mapping (and for Triton: mapping expanded * From the NAS NRC study: New Frontiers beyond Voyager with improved resolution) in the Solar System: An Integrated Exploration – Surface evolution & atmospheric structure Strategy, often called the – Magnetic field "Planetary Decadal Survey" – First compositional/spectral map From “Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets,” R. Gomes, H. F. Levison, K. – First detailed infrared map Tsiganis and A. Morbidelli 2005. Nature 435, 466-469.
Argo Science Objectives - KBO Getting to Neptune
• Option A - Jupiter-Neptune Neptune • Determine comparative properties of captured KBO – Trip time of 8-10 years Triton and a KBO in situ – Approach velocity of order 12-16 km/sec
Approach Velocity Mission Trip Time • Expand the diversity of volatile-rich (km/sec) small bodies in the outer solar system Option A 8-10 yrs 12 - 16 – Between Argo and New Horizons Voyager 12 yrs 17 (shown here) we will double the number of explored KBOs New Horizons (Pluto) 9.5 yrs 14 • Pluto Jupiter • New Horizons in situ KBO • May even have Jupiter-Saturn-Neptune Earth • Triton trajectories (under study) • Argo in situ KBO • Exploring trades between trip-time and approach velocities (next slide) Power Source Options Notional Argo Instrumentation Options
EOL (14 yrs) Preliminary suite based on science traceability matrix BOL Electric Unit Mass Estimated # Units Electric Power (W) (kg) Unit Cost Needed Power (W) • High resolution visible camera - New Horizons (NH) or reduced Cassini heritage - Alfred McEwen
MMRTG 115 103 44 $35M 3 (or even 2) • Near-Infrared spectrometer - NH heritage - Don Banfield • UV solar & stellar occ. spectrometer - reduced Cassini heritage - Amanda Hendrix ASRG 140 127 20 $20M 2 • Far-infrared linear radiometer - Diviner heritage - David Paige • Magnetometer - replaces NH dust instrument - Krishan Khurana GPHS-RTG 300 * 228 55 ? 1 (unit F-5) • Charged particle spectrometer - NH heritage
* New Horizons’ GPHS-RTG used a mix of old and new Pu; BOL power for that unit was only 240 W • Gimballed high-gain antenna - heritage radio science instrument If NF-03 AO excludes nuclear-powered missions, then no outer Solar System missions are possible other than flagship. Beyond this: explore trade space for other instrumentation in terms of If NF-03 AO is broader, missions may be possible (J-N-KBO; J-S-N-KBO). science, cost, power, and mass
UNCONVERGED TRAJECTORIES UNCONVERGED TRAJECTORIES Trojan, Triton, and KBO Triton and KBO (no Trojan)
Trojan D > 10 km, KBO D > 400 km or cold-classical Jupiter still available for 2018 launch !V optimizes down, TOF not likely to decrease by more than a year. • Red dots require upper stage