Map out nearby planetary systems and understand the diversity of the worlds they contain. Seek out nearby worlds and explore Open up new windows on the their habitability. universe from the UV through near-IR.

Habitable Exoplanet Observatory (HabEx) A starshade-only alternative

David Redding, Keith Coste, Otto Polanco, Claudia Pineda, Kevin Hurd, Howard Tseng, Stefan Martin, Rhonda Morgan, Kevin Schulz, Jonathan Tesch, Eric Cady (JPL), Michael Rodgers (Synopsis), Matthew East, James Mooney (Harris), Christopher Stark (STScI), Gordon Wu, Bradley Hood (Ball Aerospace)

Pre-Decisional Information -- For Planning and Discussion Purposes Only © 2019 California Institute of Technology. Government sponsorship acknowledged. Fitting HabEx Science into the $3-5B Cost Box

• Implement the HabEx mission concept using only a Starshade for exoplanet imaging – no coronagraph • Provides the highest quality exoplanet imaging and spectroscopy capabilities • Supports the full HabEx General Astrophysics program • But – lowers exoEarth yield, as fewer total target systems can be observed

• Eliminating the HabEx coronagraph simplifies the mission to reduce cost: • Removes a complex optical instrument • Relaxes observatory wavefront stability requirements >100 times • Permits a compact, on-axis telescope design that fits into a lower-cost launch vehicle (Vulcan Centaur, Delta IV Heavy, e.g.) • Permits use of a lower mass segmented mirror, whose manufacture is within the current state of practice • Lowers overall Observatory mass including margin to <10,000kg

• Consider decreasing aperture diameter • HabEx 3.2 S (with D=3.34m) has been our study focus, with costs <$5B • HabEx 4 S fits in the same envelope, and may also be < $5B

2 jpl.nasa.gov Pre-Decisional Information -- For Planning and Discussion Purposes Only HabEx Starshade-Only Architecture HabEx would... Seek out nearby worlds and explore their habitability. Scarfed barrel for Map out nearby planetary systems and understand pointing 40 deg the diversity of the worlds they contain. towards the Sun Open up new windows on the universe from the UV Reclosable cover through near-IR. for contamination Key Mission Requirements control Stowed Parameter Value Antenna Aperture diameter 3.2 to 4 meter Bandpass 115–1,700 nm Operating temperature ≥270K Solar Diffraction limit wavelength 400 nm Arrays

General Wavefront error, total ≤30 nm rms Pointing accuracy 2 mas/axis Radiator Pointing stability 2 mas/axis Panels Raw contrast ≤10^-10 from IWA Inner Working Angle (IWA) <74 mas Serviceability Instruments Spectroscopy resolution R ≥ 7 (300–450 nm) Door

R ≥ 140 (450–1,000 nm) Exoplanet R ≥ 40 (1,000–1,800 nm) Payload Barrel Waveband, imaging 150-1,700 nm Interface Waveband, spectroscopy 350-1,400 nm Plate

Field of View 3x3 amin Propellant Camera Camera

Workhorse Workhorse Tanks Spectral resolution R ≥2 ,000 Spacecraft Waveband 115-300 nm Bus

UV UV Field of View 2.5x2.5 amin

graph Radiators - Spectro Spectral resolution R = 1 to 60,000 Thrusters Waveband, imaging 300-1,700 nm Waveband, spectroscopy 300-1,700 nm Startrackers

Field of View 8x8 asec Camera Camera Starshade Starshade Spectral resolution R ≥2 ,000 3 jpl.nasa.gov Pre-Decisional Information -- For Planning and Discussion Purposes Only HabEx Starshade Ops Require Two Launches

4 jpl.nasa.gov Telescope Uses Active Optics for Assured Performance

SSS SMA SMA: Secondary Mirror Assembly SM: Secondary Mirror PMA: Primary Mirror Assembly SM PM: Primary Mirror RBA: Rigid Body Actuators FCA: Figure Control Actuators SMS AMS: Aft Metering Structure SSS: Secondary Support Structure SMS: Secondary Mirror Struts PIP: Payload Interface Plate

Actuator Honey Dipper Flexures (6) RS PMA (Reaction Structure) AMS Actuator Shaft Support Struts Mirror Segment Instruments Electronic Boxes

PIP Requirement 18.0 nm rms WFE Nominal Corrected Margin 8 nm • Wavefront Sensing and Control establishes 56.0 16.0 nm initial 30 nm RMS WF error Nominal Corrected Segment Figure 108.0 12.0 nm • Rigid-body control of PM segments and SM Includes effects of polishing, testing, gravity sag prediction, temperature change, coating, and phase and collimate the telescope matching radius of curvature

• PM segment figure control assures Nominal Corrected Mounting Errors 26.0 10.0 nm performance while relaxing fabrication reqts. Includes effects of bonding mounts and devices, material creep, desorption, etc. • Laser Metrology is used to continuously maintain optical alignments 5 jpl.nasa.gov ULE Mirrors: Demonstrated Performance • MMSD low mass: 10 kg/m2 •Prefer 20 kg/m2 for HabEx B • WF error: •15 nm RMS WFE stand-alone, with backouts •8 nm WFE RMS post-actuation predicted • Survivability tested to high level • Random vibe and shock

6 jpl.nasa.gov Harris Capture Range Replication

• Capture Range Replication uses precision mandrels and low-temperature slumping to replace traditional generate- grind-polish processes Flat Polished Plates LTF Flat Mirror CRR Mirror

Flat ULE Flat Grind & Plates- Front Polish • CRR finishes a mirror blank to and Back

Capture Assemble within capture range for final Range MRF or Ion and LTF Final Test Replication Finishing Mirror finishing (MRF or Ion Beam) (CRR) Flat ULE AWJ Flat Grind & Plates- Lightweight Polish • Result is a repeatable, efficient Cores Cores process for mirror fabrication, saving time and cost Large Optics w/ Deterministic

Finishing Replication

e

e

l

l

u

u d

d Ion

e

e h

h MRF

c

c

S S

CRR mirror finished under IRAD funding Custom Tooling

/

/ t

t High Labor Content

s High Precision Mandrel s

Non-Deterministic o

o Mandrel Test Set C C Replication Risk Management

Generate Grind Polish Finish Precision Precision

Capture Range Replication (CRR) leverages the strengths of replication to eliminate the high cost/ schedule processes in optical fabrication to provide an optimized solution HabEx Instruments, Minus the Coronagraph

TwTwoo--MiMirrrror Telleessccooppee HabEx Workhorse Camera HabEx Starshade Instrument Field 1 Field 2 UVS Field 3 Field 4 And And And Or Imager UV Spectrograph Starshade Spectrograph (external) Imager R = 2000 Microshutter And And Microshutter Array Array Or Or Or Grating Set Guide Grism Or R=1, 500, 1000, Imager Or Filters Grisms 3000, 6000, 12000, Channel R = 7 Guide Imager 24000, 60000 Channel Or

VIS IFS IR IFS VIS Camera IR Camera 450-1000 nm 975-1800 nm UV Detector VIS Detector IR Detector UV Detector UV Detector 450-1000 nm 975-1800 nm 320-450 nm 450-950 nm 950-1800 nm 115-300 nm 200-450 nm R=140 R=40

• Two-mirror telescope is designed to minimize the number of bounces into the UV instruments • Starshade Instrument (SSI) provides spectroscopic and guider modes in the UV, VIS and NIR bands • UV Spectrograph (UVS) provides high-resolution spectroscopic, photometric and imaging modes in the 115-300 nm band, to cover a 3 amin field • HabEx Workhorse Camera (HWC) provides imaging, photometric and spectroscopic modes in the UV, VIS and NIR, covering a 3 amin field

8 jpl.nasa.gov Starshade Instrument (SSI) For high contrast observations and SS guiding To seek out nearby worlds and explore their habitability. To map out nearby planetary systems and understand the diversity of the worlds they contain.

From the telescope

UV imager VIS imager FPA FPA Vis IFS FPA IR IFS FPA Prism PIL IR imager Vis IFS PIL FPA • Starshade Instrument has 8 modes, lenslets

covering the full λ=200-1800 band in the IR IFS lenslets Selector same 8x8 asec field. mirrors • 3 star imaging (UV, Vis and IR), • 2 IFS (Vis and IR) • 1 spectrograph (UV) • 2 pupil imaging for guiding (UV and IR) 9 jpl.nasa.gov HabEx3.2S Starshade Imaging Performance

Sunshade contrast Our solar system as seen face on from 10 parsec by Contrast, λ=300nm HabEx3.2S + Starshade -150 FoV = 8x8 arcsec, λ = 400-700 nm -100 1x zodiacal dust

-50

0 Saturn

50 Contrast Venus

HabEx Starshade fromAnglestar(mas) Jupiter 100 Diameter 52m Earth Petal Length 16m 150 Minimum F 8.8

Baseline (VIS) Mode Contrast, λ=1000nm Bandpass 300-1000nm -150 IWA0.5 58 mas Distance 76,600 km -100 Glint from SS UV Mode, small IWA -50 edge Bandpass 200-667nm

IWA0.5 39 mas 0 Distance 114,900 km 50 Contrast Starshade

IR Mode, large IWA outline Angle from star (mas)starfrom Angle Bandpass 540-1800nm 100 IWA 104 mas 0.5 150 Stellar Distance 42,600 km leakage Credit: S. Hildebrandt, S. Shaklan • Starshade provides a range of observational capabilities, all with high contrast • Recent lab results (J. Kasdin et al) demonstrate <1e-10 SS contrast performance

10 jpl.nasa.gov Starshade-Only CONOP and Yield

HabEx 4H HabEx 4S HabEx 3.2S Architecture: 4-meter Hybrid 4-meter SS-only 3.2-meter SS-only • SS-only CONOP: Exoplanet Yield: Exo-Earths: 8 5 4 • Spectrally characterize all Rocky: 55 29 23 discovered exoplanets Mini-Neptunes: 60 48 40 Giants: 63 63 56 • Return 3x to measure orbits Effective Collecting • SS-only exoplanet yield could Area (휆=200 nm): 14X HST 18X HST 12x HST

be increased, up to ~2x: Spatial Resolution • By precursor RV surveys (휆=400 nm): 25 mas 25 mas 30 mas

sensitive enough to identify Number of TRL 4 promising targets technologies: 11 7 7 • By RV follow-up to measure orbits • By refueling the SS, to give it longer life and more observations • By flying another SS • By increasing aperture size • SS-only astrophysics and solar system science also would benefit if aperture is increased

11 jpl.nasa.gov UV Spectrograph

To probe the lifecycle of baryons by determining how the gaseous processes at work in the IGM and CGM drive galactic evolution. To probe the physics governing star-planet interactions by investigating auroral activity on gas- and ice-giant planets within our solar system. Relative Transmission of Hi-Resolution UV Spectrographs

400200 4.0 5-bounce HabEx 150 4.0 300 7-bounce HabEx 3.2 5-bounce HabEx 200100 COS FUV 90-215 nm 10050 COS NUV 170-320 nm 00 90 140 190 240 290 340 • A high-throughput, 5-bounce spectrograph, with 3 amin FOV • Covers λ=115-320 nm waveband • Spectral modes with R = 500, 1000, 3000, 6000, 12000, 24000 and 60000; plus imaging and photometry • Microshutter array for multiplexed source selection and spectroscopy 12 jpl.nasa.gov HabEx Workhorse Camera To understand and trace the origin of the elements from the first stars until today. To constrain dark matter models through studies of gas and resolved stellar populations in nearby dwarf galaxies. To study planetary exospheres, cryovolcanism, and atmospheric composition within our solar system.

• A high resolution imager with three channels: UV channel covering 300-450 nm; Vis channel covering 450-950 nm; IR channel covering 950-1800 nm wavebands. • FOV is 3x3 arcmin for all channels, diffraction limited at 400 nm. • Flip-in grisms for spectroscopy to R=1000. • Microshutter array in Vis/IR path for source selection. 13 jpl.nasa.gov Wavefront Maintenance On-board feedback control Thermal/structural maintains optimal alignment. On-Orbit disturbances Maintaining Alignments Metrology subsystem Rigid body PM/SM Phasemeter actuators Optics RBA Metrology • Laser Metrology (MET) measures SM-PM- commands measurements (0.1 Hz) Pose (1 kHz) Rigid body error MET/WFC Instrument Bench alignments in real time controller Electronics

Optimal rigid Focus diverse • Rigid Body Actuators move the SM and body pose Wavefront Calibration star images WFSC determines the optimal (Once/week) PM segments to preserve alignments rigid body configuration. Wavefront Sensing and Control Laser Distance Gauge measures On the ground distance to <1 nm accuracy Laser Truss combines Beam • MET technology Launcher gauges to measure 6DOF originally developed for alignment of all optics wrt Space Interferometry corner cubes on the SM Mission Beam Launcher Fiducial Corner Cube • Elements flown on LISA Retroreflector Fiducial Pathfinder and GRACE • Probe beam from the beam Follow-On launcher is reflected by corner cube • Requires: • Returning probe beam mixes with a reference beam within the beam • Laser frequency stability to launcher <1 MHz • Phasemeter electronics measure • Temperature control of all phase between the reference and optical elements to <0.2C return beams • RBA precision <5 nm

jpl.nasa.gov Secondary Mirror Passive Thermal Design Thermal Can

Radiator panel sets A and D are equivalent to each other. Both sets consist of two st 1 Stage: 240K stacked radiator panels that will be used to Area: 5.5m^2 cool instruments of operating temperatures of 273K and 150K Primary Mirror Thermal Can 3rd Stage: 55K AreaB + C: 9m^2 Heat Pipes Routing A B C D 2nd Stage: 130K Radiator panel sets B and C are equivalent Area A + D: to each other. Both sets consist of three 4.3m^2 stacked radiator panels. The panel closest to space will be used to cool instruments of operating temperatures of 77K. The panels stacked behind are used as insulators from the hot barrel. Thermal Manifold Instruments • Heat pipes in isolated routing manifolds channel excess heat from instrument detectors, electronics and structures to the radiator • Three radiator stages operate at 240K, 130K and 55K, providing purely passive cooling for instrument electronics and detectors • Heaters in thermal cans stabilize PM segments and the SM at 270K 15 jpl.nasa.gov Instruments are Packaged for Servicibility

FGS Electronics “Spherolinder” Alignment system (above each structural flexure) FGS B (end view) Thermal straps Guide tray

Jackscrew drive Jackscrew points

Optical Thermal interface plate/ Heat pipe interface block Heat pipes

Structural Electronic Thermal 150K thermal flexures interface plate/ Pillow blocks manifold Fine Guider B 70K thermal Heat pipe interface manifold block Guide tracks Aft Metering FGS B (top view) Structure (AMS) • Instruments are designed to be replaced by a servicing spacecraft with robot arms • Servicing doors allow on-orbit access to the instrument bay • Instruments are self-contained, including electronics • Instruments are kinematically mounted using Spherolinder ball and channel system, preloaded using jack screws, with separate thermal and electronic interfaces • Guide tracks allow for controlled removal/replacement 16 jpl.nasa.gov Ball-Designed HabEx3.2S Bus

Barrel Payload Radiator Propellant Tanks Star trackers Stowed HGA Micro-G Solar array panels panels Antenna Thrusters

Primary mirror cover Monoprop Bus Thrusters Radiator panels

Grapple fixture Figure ???. Bus system overview.

Payload Interface Plate

⦰1144mm Grapple barrel structure Separation plane Payload interface fixtures Hydrazine (4X) tanks 1144mm

pressurant tanks Marmon band clamp Launch Vehicle 1707mm Adaptor (LVA) High Gain Antenna Payload Adaptor Fixture (PAF) (stowed) HydrazineHydrazine Fill and Drain thrustersthrusters ((4X)4X) Radiator valves Micro-thrusters (4x) Star trackers panels Grapple features (4X) • Bus is conventional design, except for use of microthruster attitude control • Analysis shows low disturbance, high accuracy pointing performance jpl.nasa.gov Scaling from 3.2 to 4 Meter Aperture HabEx3.2S: 3.34 m HabEx4S: 4 m aperture aperture

Barrel

HabEx4S HabEx3.2S • Telescope, instruments and associated

structures grow by 25% Solar Array • Barrel sunshade grows only slightly 3-stage • Flat door replaced with split-scarf door 10m2 Radiator Radiator for used with active passive • 3-stage radiator no longer fits, so coolers cooling cryocoolers needed for NIR detectors • Observatory mass and volume remain within Delta IV Heavy and Vulcan Servicing Doors Centaur capabilities • HabEx3.2S: 7,280kg • HabEx4S: 8,580kg Spacecraft Bus jpl.nasa.gov Launch Vehicle Accomodation

HabEx3.2S HabEx4S Scaling to 6 meters Vulcan Centaur Vulcan Centaur SLS Block 1 Single-Hinged Door Split-Scarf Door Split-Scarf Door

Vulcan Centaur Vulcan Centaur 40 deg scarf 40 deg scarf 40 deg scarf

SLS-1B

Door closed Door closed Door closed

Latched for operation Latched for operation Latched for operation

19 jpl.nasa.gov HabEx3.2S Master Equipment List (MEL)

• Current Best Estimates (CBEs) are based on CAD model, plus actuals where known • JPL standard uncertainty factor for pre-project phase is added to the CBEs to estimate total mass • Adding uncertainty factor of 43% of CBE yields a total estimate containing 30% margin

• Predicted HabEx3.2S wet mass of 7280 kg is well within 10,000 kg Delta IV Heavy and 13,400 kg Vulcan Centaur capabilities to L2

• HabEx4S MEL (not shown) totals to a predicted mass of 8580 kg, also well within LV capabilities

20 jpl.nasa.gov jpl.nasa.gov HabEx3.2S Wavefront Error Budget Total WFE Strehl Ratio 0.8 30nm Wavelength (um) 0.4 WFE (nm RMS) 30

Total WFE Reserve 27nm 14nm

OTA Static WFE WFSC WFE Instrument WFE WFE Drift 18nm 11nm 12nm 10nm

PM Figure Errors WF Sensing Instrument Static OTA Figure Drift 18nm 5nm 2nm 5nm

SM Figure Errors WF Control Field Variation Instrument Drift 2nm 10nm 12nm 4nm

OTA Misalignment Primary Mirror (PM) segments Metrology 0nm 8nm are the tall tent pole... • Post-control WF error budget • WFSC acts to correct initially large alignment and figure errors • MET + WFC continuously maintain alignments 22 jpl.nasa.gov Technology Crossovers to LUVOIR and iSAT

• Active optics • Segmented coronagraphs • HabEx S is a “single raft” iSAT precursor

jpl.nasa.gov Monolithic Primary Mirror Alternative

jpl.nasa.gov Imaging an exoEarth Candidate HabEx Starshade Name RM12 preliminary Diameter 72m 52m Petal 16m 16m Length Minimum F 10 8.8

Bandpass 150-500nm 150-500nm IWA 30mas 35mas Distance 251,519 km 153,200 km

Bandpass 300-1000nm 300-1000nm IWA 60mas 70mas Distance 125,760 km 76,600 km

• HabEx Interim Report Starshade is 72 m • A solar system analog as seen • F = 10 design, with 16 m petals from 5 pc by HabEx + Starshade (a)an exoEarth • Broadband: λ = 300-1000 nm (b)a sub-Neptune • Alternate Starshade designs are currently under study (c)Jupiter, (d) Saturn, (e) • IWA = 60 to 70mas Neptune • Diameter = 52 to 59 m • Inner dust belt (3x zodiacal dust within 1 AU) • Distance = 76,600 to 101,400 km for 흺 = 300-1,000 nm • Outer dust belt (3x Kuiper belt • Knowing where to look would improve efficiency extending 22 to 33 AU) • Precursor RV surveys may identify target systems in • FoV = 12x12 arcsec advance, boosting Starshade-only exoEarth yield Credit: S. Hildebrandt

jpl.nasa.gov Fitting HabEx Science into the $3-5B Cost Box Starshade (SS) or coronagraph – pick one! • SS offers better high-contrast imaging and spectroscopy, and is the tool of choice for exoplanet characterization • Full bandpass (300-1000nm, e.g), vs. 10-20%, and higher throughput • Full field, 8 asec vs. 1 asec enables imaging of nearby outer planets • But – need to maneuver SS means fewer exoEarths discovered • Coronagraphs are better at searching for planets • Changing targets takes hours, not days • But limited bandpass (10-20%) and throughput means it takes longer to characterize exoplanet targets • Field of view is limited by narrow Outer Working Angle, limiting discovery space

jpl.nasa.gov Wavefront Sensing and Control (WFSC) • Image-based sensing methods are used to align the telescope after launch and achieve initial, diffraction limited performance • Uses methods developed and demonstrated for JWST and SIM

PSF images from each segment are identified Phase (MGS) and Prescription Retrieval (IPO) and incoherently stacked on the focal plane. methods produce high resolution wavefront maps for detailed alignment. Dispersed Fringe Sensing (DFS) is used to coherently phase segment pairs.

Metrology beams acquired using M1/M2 spiral scan. Once aligned, closed-loop Power maximized using Metrology control maintains dithering algorithm. optical alignments

1mm 100µm 10µm 1µm 100nm 10nm RMS WFE AssemblyMetrology Capture

Alignment CaptureCoarse Alignment 40 nm Shack-Hartmann Dispersed FringeCoarse Sensing Phasing Fine Phasing Relative Laser Metrology jpl.nasa.gov Commissioning and Initial Alignment Wavefront Sensing • Image-based sensing methods are used to align the telescope after launch and achieve initial, diffraction limited performance. • Detailed commissioning timeline in development.

PSF images from each segment are identified Phase (MGS) and Prescription Retrieval (IPO) and Control (WFSC) and incoherently stacked on the focal plane. methods produce high resolution wavefront maps for detailed alignment.

Dispersed Fringe Sensing (DFS) is used • Wavefront Sensing and Control to coherently phase segment pairs.

(WFSC) establishes exquisite Metrology beams acquired using M1/M2 spiral scan. Power maximized using optical quality after launch dithering algorithm. 1mm 100µm 10µm 1µm 100nm 10nm RMS WFE • Laser Truss metrology (MET) AssemMbelytrology Capture Alignment CaptuCroearse Alignment 40 nm Shack-Hartmann preserves optical quality during Dispersed FCrionagrese S Pehnassiing Fine Phasing all operations Relative Laser Metrology

Laser Metrology Overview Laser Metrology Truss • 6 or 9 Laser gauges per optic Beam Launcher • Optic is referenced to the optic bench • Excellent sensitivity in the optically

significant degrees of freedom (θX, θY, ΔZ) Beam Launcher (BL) Placement - Largest possible spacing between BLs - BLs do not impact gap between segments Wavefront Error Due to Pose Changes

Beam Launcher Fiducial Corner Cube Retroreflector Fiducial

• A collimated beam from the Beam Launcher (BL) propagates through free space and to a corner cube, then back to the BL where it couples back into fiber optics. Pose Uncertainty per nm of laser gauge uncertainty (9BL Config) • A portion of the beam is also reflected from the BL and coupled back into the optic fiber. ΔX ΔY ΔZ θX θY θZ • A heterodyne technique is used to measure changes in the phase between the two paths. Segment (nm or nrad) 8.2 10.4 0.50 2.6 2.2 8.6 SM (nm or nrad) 8.8 9.1 0.33 2.1 1.8 30.6 4/1/2021 28 Launch Vehicle Acommodation

HabEx3.2S HabEx3.2S HabEx4S Vulcan Centaur DELTA IV Heavy Vulcan Centaur Single-Hinged Door Split-Scarf Door Split-Scarf Door

40 deg scarf Vulcan Delta IV Vulcan Centaur Heavy Centaur 40 deg scarf 40 deg scarf

Door closed Door closed Door closed

Latched for operation Latched for operation Latched for operation

29 jpl.nasa.gov HabEx Starshade-Only Architecture

Scarfed barrel for pointing 40 deg towards the Sun

Reclosable cover for contamination Stowed control Antenna

Solar Arrays

Radiator Panels

Serviceability Instruments Doors

Payload Barrel Interface HabEx would... Plate Propellant Tanks Seek out nearby worlds and explore their habitability. Spacecraft Map out nearby planetary systems and understand Bus the diversity of the worlds they contain. Radiators Open up new windows on the universe from the UV Thrusters through near-IR. Startrackers

30 jpl.nasa.gov Pre-Decisional Information -- For Planning and Discussion Purposes Only