A Large Aperture Deployable Telescope for the Next UV/Optical Telescope (NHST) Mission

C. F. Lillie Next Large Aperture Optical/UV Telescope Workshop 11 April 2003 Next Large Optical/UV Telescope Workshop

Science Objectives

ƒ Continue to obtain the UV-Optical observations begun with HST, with much higher resolution (3-6 milli-arcseconds) and sensitivity (<1 nano-Jansky) – Galactic star formation – Formation and evolution of galaxies and clusters – Quasars and black holes – Cosmology ƒ Connect the high-redshift universe observable with SIRTF and JWST to the low - redshift universe that NHST can study in detail with wide-field imaging and high resolution spectroscopy by: – Measuring the density and distribution of baryons and large scale structure – Detecting unseen matter in the modern universe – Understanding the chemical evolution of the elements – Observing the major construction phase of quasars and galaxies ƒ Detect and characterize planets around nearby stars

2 Next Large Optical/UV Telescope Workshop

Design Begins With Top-Level Requirements

Requirement Parameter Source Class I Mission Class II Mission Orbit Geosynchronous or L2 Geosynchronous or L2 WP Spectral resolution 1,000 plus 5,000 to 10,000 and 1,000 plus 5,000 to 10,000 and WP 30,000 to 50, 000 30,000 to 50, 000 a goal of 50,000 to 200,000 a goal of 50,000 to 200,000 Aperture 4.2 meters 8 meters WP Effective Area >2.0 m2 (10 x HST/COS) >10.0 m2 WP Spectral Multiplexing ≤ 2 integrations at R=30,000 ≤ 2 integrations at R=30,000 WP Spatial Resolution 30 mas at 500 nm required 15 mas at 500 nm WP, NGST <10 mas at 115 nm goal <5 mas at 115 nm goal Wavelength Coverage 115-320 nm for spectroscopy 115-320 nm for spectroscopy WP 200-1000 nm for imaging (115-1000 200-1000 nm for imaging (115-1000 nm goal) nm goal) 350-1000 nm for integral field 350-1000 nm for integral field Field of View 13.6 x 17.9 arc minutes 12.3 x 15.8 arc minutes WP Imaging CCD for tracking/acquisition, plus CCD for tracking/acquisition, plus WP 16K2 for WF and Hi-res imaging 24K2 for WF and Hi-res imaging Discovery Efficiency ≈ 100 to 480 ≈ 500 to 1760 WP Launch Date 2010 2012 WP, NGST Mission duration 5 years, 10 year goal 5 years, 10 year goal WP Mission Cost Target $450M WP

WP refers to UVOWG White Paper; NGST refers to requirements derived by Northrop Grumman Space Technology 3 Next Large Optical/UV Telescope Workshop Requirements Flowdown Process Refines Requirements

Mission Phenomenology Requirements

Galaxies & Clusters, Stars & planets Quasars & IGM SNR for detection Target SNR for List characterization UV wavelength range VIS wavelength range

Mission duration Background Target Characteristics emissions Contrast ratio Angular size Max time per target Star-Planet Separation Distribution on sky

Operational scenario development, performance modeling, and system sizing

Coronagraph Telescope Data rate Integration time Slew rate spot size temperature

Spectral Aperture Pointing control Field of view Field of regard resolution 4 Next Large Optical/UV Telescope Workshop

A Single Requirement Can Impact Many Areas

Average Separation of Number of Slew Time Slew Rate RWA Size Targets Duration of Targets Mission Flight System Settle Time Telescope Dynamics Stiffness

Distribution of Targets Sunshield Stiffness

Sky Integration FPA Read Coverage Size of Readout Time Noise Data Habitable Zone Rate Storage

Types of Data Rate Stars Data Slew Angular Size of Planet Orbit Processing Range Performance of Target Telescope Brightness

Aperture Sunshield Dimensions Thermal WFE Control Collecting Spot Size Telescope Area Deployment

Sunshield Coronagraph Deployment Deformable Performance Manufacturing Mirror Schedule Number of Mirror Segments 5 Next Large Optical/UV Telescope Workshop Candidate NHST Optical Configuration

ƒ TMA provides Wide FOV with few Primary Mirror with 6 to 36 Replicated Segments and surfaces for high throughput Protected Al Coatings ƒ Simple on-axis conic prescription avoids costly fabrication, provides 6-7 m flat-to-flat generous alignment tolerances ƒ Fine Steering Mirror eliminates low Tertiary frequency motion, provides FOV Mirror offsets (dither), and offloads large angles to spacecraft ACS Focal Surface ƒ Segmented deformable mirror Interface to corrects for higher order uncorrected Instrument Module Wave Front errors FSM/ ƒ Simple, clean interface keeps AI&T Segmented DM Telescope LOS and verification costs low Secondary Mirror

Replicated ROC Actuator Mirror (in center) • Mid-high frequency optical quality manufactured into segments • Segments fully tested before OTE assembly • System optic performance end-to-end test at operating temperature prior to launch Actuators simplify wave front sensing & control system • Tip, tilt, piston, and ROC control Force • Rigid body motion independent of ROC control Reaction • Rigid body corrections do not induce surface Tip/Tilt/Piston Actuators Structure at corners distortions or stress Actuators 6 Next Large Optical/UV Telescope Workshop Hex-Mirror Actuator Sensitivity Study Defines NHST Needs

ƒ Actuator density study shows Actuator Quantity Trades: seven force actuators are Figure Correct ability vs. Number of Actuators ample for correcting low order 100% deformations: 90% – RoC, astigmatism, trefoil 80%

nt rms) 70% – Using Global Influence e

erc 60% Functions to control mid- p

spatial frequencies from 0.5 to 50% Power

~ 10 cycles/diameter ction ( Astigmatism 40% Trefoil – Residual is corrected by DM 30% with 200 actuators/diameter gure Corre Moments at 20% ƒ Coronagraph requires Fi Mounts 10% correction of spatial 0% frequencies in the band from 147101316 ~0.8 to 98 cycles/diameter Number of Actuators

7 Next Large Optical/UV Telescope Workshop Deployable UVO Telescope

• Segmented UV-Optical Inflatable Sunshade Telescope 6-DOF – 7-hex, 4.5-m, primary mirror Secondary Mirror – 6 DOF secondary mirror – HARD deployment approach • Spacecraft bus design Solar derived from SSTI and T300 Array (1 of 2) 4.5 m dia. spacecraft Primary • Inflatable sunshade for stray Mirror light rejection • Launch with Delta III to L2 Instrument Module lissajous orbit High • X-band communication with Gain 0.6 m S/C antenna and 11m Antenna ground antenna Spacecraft Bus • Telescope Baffles omitted for clarity – 2 Kbps uplink, 1 Mbps return

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Stowed Configuration

• SUVO shown in 9.5’ 9.5’ Delta II diameter Delta II fairing Fairing • 1.86 m diameter payload stack also compatible with 8’ and 10’ diameter fairings • Large performance margin Inflatable with candidate launch Sunshade vehicles and orbits – 600 x 10,000 km elliptical orbit with Delta 7920 Launch Vehicle Adapter – Driftaway or L2 orbit with Delta III or Atlas III

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(Very) Large Aperture Telescope Design Concept ƒ 28-meter filled aperture telescope

– Three-mirror anastigmat 3 28-m 50m Science – 36 segments, 4-meter flat-flat Primary Instrument – Composite replica optics Module – Protected Al mirror coatings ƒ Multi-layer sunshade 6 6-DOF – Solar radiation reduced by >10 Secondary – Mirror heated to ~24±0.01° C ƒ Coronagraph for planetary detection/characterization ƒ Cameras and spectrographs for general imaging/spectroscopy – 3 x 3 arcmin FOV ƒ Launched with EELV to L2 ~35 x 50-m – Delta IV or Atlas V Multi-layer – Direct or Lunar flyby Sunshield

Design Easily Scaled to 8 or 12 meter Apertures 10 Next Large Optical/UV Telescope Workshop NHST Telescope Technology Needs

ƒ Large, lightweight optics – 5-10 kg/m2 areal density – 0.5 mm diffraction limited (0.2 mm goal) – Surface roughness < 10 Angstroms (3 Angstroms goal) – Mid-spatial frequency errors < 1 nm RMS – Lightweight, compact, nanometer resolution actuators ƒ Low-cost mirror fabrication – Thin replicated mirrors – Composite design – Mandrel production – Large segment production ƒ High reflectivity mirror coatings ƒ Large deformable mirrors – 1-2 millimeter pitch – Could be segmented, with tip/tilt piston stage for individual modules ƒ Precision deployable structure testbeds – Secondary support structures – Multi-ring primary mirrors

11 Next Large Optical/UV Telescope Workshop Composite Mirror State-of-the-Art

ƒ Mirror segments produced using replication techniques – COI 2-m FIRST demonstrator - Cervit mold polished by University of Arizona – 0.25 µm surface accuracy; 100 Angstroms smoothness - Production from 2/99-8/99 - Good wavefront performance – 2.32 µm RMS – After removing 1st 36 Zernickes, 1.00 µm RMS at room temperature • 1.21 µm RMS at 200K vs. 0.2 µm RMS at 30K requirement - Design extrapolated to 3.5 m diameter at 11.4 kg/m2 – CMA thin replicated mirrors - Pyrex mold - 15 cm spheres at 0.79 µm RMS and 1.3 kg/m2 - 90 cm sphere at 1.7 kg/m2 - Surface roughness <10 Angstroms has been demonstrated. - Mid-spatial frequency errors <3 nm RMS has been demonstrated. ƒ Composite mirror technology is on track to meet NHST requirements

12 Technology Roadmap 10-9 Next Large Optical/UV Telescope Workshop Telescope Deployment

Highly mass and volume efficient concept developed for JWST, applicable to NHST

13 Next Large Optical/UV Telescope Workshop High Accuracy Reflector Demonstration

60- 94 GHz reflector developed in1991-92 with 25 micron rms repeatability, 5 kg/m2 areal density

14 Next Large Optical/UV Telescope Workshop Multi-Ring Mirror Mirror Deployment

Automatic deployment concept expandable to much larger apertures

15 Next Large Optical/UV Telescope Workshop Summary

ƒ Segmented telescope design concepts developed for aperture sizes from 4 to 28 meters – Wide range of options for system trades and analyses – Single ring preferred for cononography ƒ Enabling technologies at Technology Readiness Level 4-5, could be ready for 2012 launch – Replica optics technology demonstrated by CMA for smaller segments o Could provide large cost and schedule reductions – Modular deformable mirrors now being developed by Xinetics – Primary mirror deployment approach demonstrated, mechanisms developed – Deployable telescope testbed needed to for system level demonstration, including secondary mirror deployment ƒ No technical “show-stoppers” identified

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