Lightweight Deployable UV/Visible/IR Telescopes

1. Lightweight Deployable UV/Visible/IR Telescopes

2. Technology Enablers to the VisionKey Characteristics • Future remote sensing instruments may need to employ large numbers of frequency-agile instruments capable of multi-scene observations. Real-time, autonomous adaptive sensing and taskability will be critical. Advanced capabilities will include: • Miniaturized observatories • Robust, compact instrument architectures • Large deployable apertures • Aperture synthesis • Miniaturized/programmable components • Low cost manufacturability

3. MotivationProgrammatic Limiters to the Vision • Length of time to plan, development and deploy space-based instruments for periodic focused measurements • The result: A decade may pass between the theoretical identification of a phenomenon and the deployment of a space-based asset limits measurement continuity and applicability • Limited budgets preclude continually launching unique instruments targeted toward specific measurement needs • The result: Instrument designs are targeted to specific measurements and consequently once deployed cannot accommodate new scientific findings

4. Lightweight Deployable UV/Vis/IR TelescopesPathway to the Vision • Science Needs: • Lidar observations for high vertical resolution mapping of tropospheric ozone, CO2, water vapor, NO2, aerosols, and for imaging, and • High resolution imaging and spectroscopic observations from high orbits (GEO, LI, and L2)

5. Lightweight Deployable UV/Vis/IR TelescopesPathway to the Vision

6. Lightweight Deployable UV/Vis/IR TelescopesProblems Unique to Earth Observing Measurements Extensive on-going work associated with NGST in deployable telescopes. Unique problems associated with typical Earth observing missions: • Thermal cycling effects due to variable solar loading, day/night transitions, thermal shock from going into and out of eclipse and pointing close to Sun line • Pointing non inertial reference frame or scene reference complicates attitude control • Doppler shifts (wavelength calibration) • Orbit maintenance, thruster issues, contamination, control law issues • Minimize structural mass with uniform and low CTE across structure with good optical surface • Active/adaptive control on Earth scenes (wide dynamic range) • Image registration (mapping, land-marking)

7. Lightweight Deployable UV/Vis/IR TelescopesProblems Unique to Earth Observing Measurements Recent advancements in mirror research have considered the following materials: • composite mirrors • carbon silicon carbide • glass/composite • thin meniscus glass • beryllium • light weighted glass • membranes (powered and flat) • fresnel lens The fundamental issues associated with these materials are their manufacturability and their subsequent integration into associated control actuators, reaction structures, and deployment systems. Other factors include filter coatings to reduce the heat load on the mirror and the ability to control the mirror in the dynamic thermal environments.

8. Lightweight Deployable UV/Vis/IR TelescopesProblems Unique to Earth Observing Measurements Structures and mechanisms are also a significant challenge for deployable telescopes. The state of the art is currently: • Mid-modulus CFRP, open truss design • USAF/RL MISTI (solid hexagonal frame) • Multifunctional structures • Isogrid vs. solid tubular frame

9. Lightweight Deployable UV/Vis/IR TelescopesSummary of Technology Approaches • • Light-weight mirrors • – glass/composite • – thin film (stretch membrane/replicated shells) • • Structures and latches • – deploy/redeploy capability • – elastic memory composite materials • • Optical alignment techniques • – active vs. passive • – deformable/correction optics • – wavefront sensing/control

10. Deployable UV/Vis/IR TelescopesVision-driven Roadmap 10000 .1 Areal Density (kg/m2) 1 1000 Array Area (m2) 50m High Resolution Imager 100 10 Adaptive Membrane Optics GEO High Resolution Thermal Imager Inflatable Antennas 100 10 Deployable Segmented Telescopes 2010 Now 2020

11. Lightweight Deployable UV/Vis/IR TelescopesNotional Validation Flight In developing a validation test plan to determine what characteristics will be tested, the following elements must be considered: • characterization of disturbance sources (e.g., sunshields, reaction wheels, fine-pointing and alignment systems) • microdynamic response of mechanically deployable support structures and active control of microdynamics • dimensional stability of thin-membrane mirrors and active wavefront correction

12. 12 FY 02 03 04 05 06 07 08 09 10 11 Tropospheric Ozone Measurement (UV)Technology Roadmap Composite Mirror Panels Salient requirement: 3m aperture Precision Latch & Hinge Deployment Mechanisms NMP - flight validation Tropospheric Ozone Measurement Capability Technology Validation Mission Salient requirements: repeatability reliability, one-time operation UV DIAL: 308/320 nm @ 10Hz; O3 vertical resolution 2.0-2.5 km in troposphere; horizontal resolution 100 km; IFOV < 100 m Diode-pumped Laser Transmitter (UV) Salient requirements: 500mJ, 308/320 nm @ 10Hz

13. Lightweight Deployable UV/Vis/IR TelescopesConcluding Remarks The science needs established by the vision of NASA’s Earth Science Enterprise challenge the state of the art for instrument technologies. A process by which technology requirements are developed begins by translating the science needs into notional measurement implementations and then defining the critical drivers for achieving the science needs. These drivers result in a set of technology requirements from which development plans can be established. A nominal space validation experiment would include fabrication of a test article of a deployable telescope structure and mating it to a microgravity test platform on the ISS. Tests of micro and macrodynamic characteristics of the structure would be conducted in order to understand and characterize the dynamic responses and deployment of the structure in zero-g. Partnerships between NASA and interagency, international, commercial and academic organizations will be essential to achieve this vision. The economic benefits will be shared across the globe.