JASMINE: Near-infrared astrometry and time-series photometry science

The Japan Astrometry Satellite Mission for INfrared Exploration (JASMINE) is a planned M-class science space mission by the Institute of Space and Astronautical Science, the Japan Aerospace Exploration Agency. JASMINE has two main science goals. One is Galactic archaeology with a Galactic Center survey, which aims to reveal the Milky Way’s central core structure and formation history from Gaia-level (∼25 ${\mu}$as) astrometry in the near-infrared (NIR) Hw band (1.0–1.6 ${\mu}$m). The other is an exoplanet survey, which aims to discover transiting Earth-like exoplanets in the habitable zone from NIR time-series photometry of M dwarfs when the Galactic Center is not accessible. We introduce the mission, review many science objectives, and present the instrument concept. JASMINE will be the first dedicated NIR astrometry space mission and provide precise astrometric information on the stars in the Galactic Center, taking advantage of the significantly lower extinction in the NIR. The precise astrometry is obtained by taking many short-exposure images. Hence, the JASMINE Galactic Center survey data will be valuable for studies of exoplanet transits, asteroseismology, variable stars, and microlensing studies, including discovery of (intermediate-mass) black holes. We highlight a swath of such potential science, and also describe synergies with other missions

Compact Dual Field-of-View Telescope for Small Satellite Payloads

Small satellite payloads commonly involve missions with multiple field-of-view (FOV) capability. For these missions, it is often desirable that the payload instrument contain optical sensors with both a wide FOV for searching or scanning a scene and a narrow FOV to interrogate and identify the object of interest. This generally requires multiple sensors or a zoom lens with multiple moving lenses. For infrared sensors, these approaches are generally not compact enough for use on small space platforms, unmanned air vehicles, or small satellite payloads. This paper describes a compact dual field-of-view telescope with a 6x field ratio. The selection of the field involves changing optical filters, which transmit different spectral wavebands. Each spectral waveband is associated with separate optical paths with differing focal lengths, thus fields-of-view. This concept has been proven through the design, build, and alignment of a long-wave infrared (LWIR) catadioptric telescope

Deployable Mirror for Enhanced Imagery Suitable for Small Satellite Applications

High spatial resolution imagery and large apertures go hand in hand but small satellite volume constraints place a direct limit on monolithic aperture mirror systems. Deployable optical systems hold promise of overcoming aperture size constraints and greatly enhancing small satellite imaging capabilities. The Space Dynamics Laboratory (SDL) is currently researching deployable optics suitable for small spacecraft and has developed a passively aligned deployable mirror. The team recently built a proof-of-principle mirror and a single parabolic mirror segment or “petal” measured for deployment repeatability. They measured elevation (tilt) and azimuth (tip) angular alignment repeatability to be 0.6 arcseconds or 2.9 μrad (1 sigma) in each axis after a ten deployment sequence. The SDL team used optical modeling to study the effects of these alignment errors on a multiple petal parabolic primary mirror part of a Cassegrain imaging system. The model indicates that excellent image quality is possible in the short wave infrared (SWIR) to long wave infrared (LWIR) bands. Work continues on a four segment deployable primary mirror with an aperture diameter of 152 mm. The goal is to fabricate the mirror segments and demonstrate repeatable interferometric wavefront error measurements

CubeSat Image Resolution Capabilities with Deployable Optics and Current Imaging Technology

Research in attitude determination and control, communications, power, and propulsion of CubeSats are making advances every year. Advancement in these areas of technology are required for CubeSats to be capable of increased resolution imagery. One aspect of CubeSats, and all other small satellites, remains constant: their limited volume. The volume ultimately limits the size of an optical payload. A brief survey of current Earth optical imaging satellites shows the importance of aperture size to obtain the spatial resolution required to achieve mission objectives. The Space Dynamics Laboratory (SDL) is researching deployable optical apertures in order to overcome the volume constraint on aperture diameter and telescope focal length. To date, SDL has demonstrated successful deployment repeatability of optical mirror segments and metering structures that are capable of supporting high-resolution imagery in the visible spectrum. The paper concludes with a conceptual CubeSat high resolution imager that incorporates deployable optics and current imaging technology

Slanted-edge MTF Focus Test Verification with PRF Testing to Establish Best Focus Position of Infinite Conjugate Space Optical Systems

For earth-viewing, fixed-focus space optical systems, carefully finding the best focus position of the instrument is critical to achieving the best possible image performance and mission success. For such space optical systems, modulation transfer function (MTF) test data is directly applicable to system optical resolution. Furthermore, MTF test products can be combined to predict overall imaging performance. The infinite conjugate slanted edge MTF test can be used in ground testing to identify best focus of the optical system while taking into account the entire imaging system, operational parameters, and simulated operational environment. The point-response function (PRF) test can be used to verify the results of the slanted edge MTF test to ensure that the optimum best focus position is determined. This paper discusses the slanted edge MTF test for establishing best focus and the PRF test for verifying the best focus. Actual MTF and PRF test results are presented

Fine Steering Mirror for Smallsat Pointing and Stabilization

SDL has used internal funds to develop a prototype low-cost 2-axis fine steering mirror (FSM) as an enabling technology for smallsats. The FSM has a lightweight high-reflectance mirror, high angular deflection capability for along-track ground motion compensation and cross-track pointing, and a high bandwidth to help cancel unwanted jitter. Key performance parameters areClear aperture, 75 mm; along-track angle, ±30 deg (mechanical); cross-track angle, ±60 deg (mechanical); slew rate, greater than 75 deg/sec; bandwidth, 70 Hz; steadystate average error, as good as 1 arcsec; average power dissipation, 0.4 Watts; and total mechanical mass, 1 kg. The FSM makes use of off-the-shelf components as much as possible. Key components for the along-track (elevation) axis include a rotary voice coil and a unique non-contact feedback sensor. The cross-track (azimuth) axis features a brushless DC motor and a high-resolution optical encoder. Rapid prototyping, autocoding, and real-time hardwarein- the-loop (HIL) testing were used to develop the control algorithms. The cost for the first prototype (including labor and materials) was about $200K

Test Validated Alignment and Stability Performance of the JMAPS Program Focal Plane Array Assembly in a Cryogenic Vacuum Environment

Focal Plane Arrays (FPA) consisting of multiple Sensor Chip Assemblies (SCA) in a precision aligned mosaic are being increasingly used in optical instruments requiring large format detectors. The Joint Milli-Arcsecond Pathfinder Survey Mission (JMAPS) requires very precise positional alignment and stability of its 2 x 2 SCA mosaic at operational temperatures to meet its precision sky mapping mission requirements. Key performance requirements include: detector active area co-planarity, in-plane alignment, and thermal stability. This paper presents an overview of the JMAPS Focal Plane Array Assembly, its alignment and thermal-mechanical stability requirements, and associated test-validated performance in a cryogenic vacuum environment

Optical Coating Characterization System (OCCS) Design and Qualification

The Space Dynamics Laboratory, under contract to the Missile Defense Agency, designed and built the optical coating characterization system (OCCS) cryogenic system for spectral (FTIR) measurement of optical transmittance and reflectance at temperatures of 90 K and higher. The OCCS is designed to make cryogenic transmittance measurements from normal up to a 50 degree angle-of-incidence, and reflectance measurements between 40 and 50 degrees angle-of-incidence, in a converging optical beam of F/2 or greater. The system can measure up to 20 1-inch diameter optical components in a single cold cycle, or fewer larger components with flat surfaces up to 3 inches in diameter. This presentation will provide a brief overview of the OCCS design, followed by test results showing the performance achieved during qualification measurements