Robert A. Laskin

SIM technology development overview: light at the end of the tunnel

Optical and IR interferometry wil open new vistas for astronomy over the next decade. Space based interferometers, operating unfettered by the Earths atmosphere, will offer the greatest scientific payoff. They also present the greatest technological challenge: laser metrology systems must perform with sub-nanometer precision; mechanical vibrations must be controlled to nanometers requiring orders of magnitude disturbance rejection; a multitude of actuators and sensors must operate flawlessly in concert. The Jet Propulsion Laboratory along with its industry partners, Lockheed Martin and TRW, are addressing these challenges with a development program that plans to establish technology readiness for the SIM by the end of 2004.

Successful completion of SIM-PlanetQuest technology

Optical interferometry will open new vistas for astronomy over the next decade. The Space Interferometry Mission (SIM-PlanetQuest), operating unfettered by the Earths atmosphere, will offer unprecedented astrometric precision that promises the discovery of Earth-class extra-solar planets as well as a wealth of important astrophysics. Optical interferometers also present severe technological challenges: laser metrology systems must perform with sub-nanometer precision; mechanical vibrations must be controlled to nanometers requiring orders of magnitude disturbance rejection; a multitude of actuators and sensors must operate flawlessly and in concert. The Jet Propulsion Laboratory, with the support of Lockheed Martin Advanced Technology Center (LM ATC) and Northrop Grumman Space Technology (NGST), has addressed these challenges with a technology development program that is now complete. Technology transfer to the SIM flight team is now well along and the project is proceeding toward Preliminary Design Review (PDR) with a quickening pace.

Separated-spacecraft interferometer concept for the New Millennium Program

A separated spacecraft optical interferometer mission concept proposed for NASAs New Millennium Program is described. The interferometer instrument is distributed over three small spacecraft: two spacecraft serve as collectors, directing starlight toward a third spacecraft which combines the light and performs the interferometric detection. As the primary objective is technology demonstration, the optics are modest size, with a 12-cm aperture. The interferometer baseline is variable from 100 m to 1 km, providing angular resolutions from 1 to 0.1 milliarcseconds. Laser metrology is used to measure relative motions of the three spacecraft. High-bandwidth corrections for stationkeeping errors are accomplished by feedforward to an optical delay line in the combiner spacecraft; low-bandwidth corrections are accomplished by spacecraft control with an electric propulsion or cold-gas system. Determination of rotation of the constellation as a whole uses a Kilometric Optical Gyro, which employs counter-propagating laser beams among the three spacecraft to measure rotation with high accuracy. The mission is deployed in a low-disturbance solar orbit to minimize the stationkeeping burden. As it is well beyond the coverage of the GPS constellation, deployment and coarse stationkeeping are monitored with a GPS-like system, with each spacecraft providing both transmit and receive ranging and attitude functions.

Space Interferometry Mission (SIM): technology completion and transition to flight

Optical interferometry will open new vistas for astronomy over the next decade. The Space Interferometry Mission, operating unfettered by the Earths atmosphere, will offer unprecedented astrometric precision that promises the discovery of Earth-class extra-solar planets as well as a wealth of important astrophysics. Optical interometers also present severe technological challenges: laser metrology systems must perform with sub-nanometer precision; mechanical vibrations must be controlled to nanometers requiring orders of magnitude distrubance rejection; a multitude of actuators and sensors must operate flawlessly and in concert. The Jet Propulsion Laboratory along with its industry partners, Northrop Grumman Space Technology, and Lockheed Martin, are addressing these challenges with a technology development program that is nearing completion. Emphasis is shifting from technology demonstration to technology transfer to the flight team that wil build and launch the space system.

Multiaxis vibration isolation, suppression, and steering system for space observational applications

THe paper describes an actively controlled six-axis orthogonal hexapod mount that provides vibration isolation, suppression and steering capabilities for space observational systems. Experimental results for vibration isolation is presented. The results show that though the passive-only isolation reduces disturbance propagation significantly, the combination of active and passive isolation provides the best option. The active stage reduces the propagation over the passive-only case by additional 35 dB in the mid frequency range of 10-100Hz.

Technology for space optical and infrared interferometry

Optical and IR interferometry will open new vistas for astronomy over the next decade. Space based interferometers, operating unfettered by the Earths atmosphere, will offer the greatest scientific payoff. They also present the greatest technological challenge: laser metrology systems must perform with sub-nanometer precision; mechanical vibrations must be controlled to nanometers requiring orders of magnitude disturbance rejection; a multitude of actuators and sensors must operate flawlessly and in concert. The interferometry technology program at NASAs JPL is addressing these challenges with a development program that plans to establish technology readiness for the Space Interferometry Mission by early in the year 2001.

Space Interferometry Mission: measuring the Universe

The Space Interferometry Mission (SIM) will be the NASA Origins Programs first space based long baseline interferometric observatory. SIM will use a 10 m Michelson stellar interferometer to provide 4 /spl mu/as precision absolute position measurements of stars down to 20th magnitude over its 5 yr. mission lifetime. SIM will also provide technology demonstrations of synthesis imaging and interferometric nulling. This paper describes the what, why and how of the SIM mission, including an overall mission and system description, science objectives, general description of how SIM makes its measurements, description of the design concepts now under consideration, operations concept, and supporting technology program.

SIM Planetquest Science and Technology: A Status Report

Optical interferometry will open new vistas for astronomy over the next decade. The Space Interferometry Mission (SIM-PlanetQuest), operating unfettered by the Earths atmosphere, will offer unprecedented astrometric precision that promises the discovery of Earth-analog extra-solar planets as well as a wealth of important astrophysics. Results from SIM will permit the determination of stellar masses to accuracies of 2% or better for objects ranging from brown dwarfs through main sequence stars to evolved white dwarfs, neutron stars, and black holes. Studies of star clusters will yield age determinations and internal dynamics. Microlensing measurements will present the mass spectrum of the Milky Way internal to the Sun while proper motion surveys will show the Suns orbital radius and speed. Studies of the Galaxys halo component and companion dwarf galaxies permit the determination of the Milky Ways mass distribution, including its Dark Matter component and the mass distribution and Dark Matter component of the Local Group. Cosmology benefits from precision (1-2%) determination of distances to Cepheid and RR Lyrae standard candles. The emission mechanism of supermassive black holes will be investigated. Finally, radio and optical celestial reference frames will be tied together by an improvement of two orders of magnitude. Optical interferometers present severe technological challenges. The Jet Propulsion Laboratory, with the support of Lockheed Martin Advanced Technology Center (LM ATC) and Northrop Grumman Space Technology (NGST), has addressed these challenges with a technology development program that is now complete. The requirements for SIM have been satisfied, based on outside peer review, using a series of laboratory tests and appropriate computer simulations: laser metrology systems perform with 10 picometer precision; mechanical vibrations have been controlled to nanometers, demonstrating orders of magnitude disturbance rejection; and knowledge of component positions throughout the whole test assembly has been demonstrated to the required picometer level. Technology transfer to the SIM flight team is now well along.

Space Interferometry Mission (SIM): meeting the technology challenge

Optical and infrared interferometry will open new vistas for astronomy over the next decade. Space based interferometers, operating unfettered by the Earths atmosphere, will offer the greatest scientific payoff. They also present the greatest technological challenge: laser metrology systems must perform with sub-nanometer precision; mechanical vibrations must be controlled to nanometers requiring orders of magnitude disturbance rejection; a multitude of actuators and sensors must operate flawlessly and in concert. The Interferometry Technology program at NASAs Jet Propulsion Laboratory is addressing these challenges with a development program that plans to establish technology readiness for the Space Interferometry Mission by early in the year 2001.

System-wide design issues for the stellar interferometer technology experiment (SITE)

The Stellar Interferometer Technology Experiment (SITE) is a near-term precursor mission for spaceborne optical interferometry. Proposed by the MIT Space Engineering Research Center and NASAs Jet Propulsion Laboratory, SITE is a two-aperture stellar interferometer located in the payload bay of the Space Shuttle. It has a baseline of four meters, operates with a detection bandwidth of 300 nanometers in the visible spectrum, and consists of three optical benches kinematically mounted inside a precision truss structure. The objective of SITE is to demonstrate system-level functionality of a space-based stellar interferometer through the use of enabling and enhancing Controlled Structures Technologies such as vibration isolation and suppression. Moreover, SITE will validate, in the space environment, technologies such as optical delay lines, laser metrology systems, fringe detectors, active fringe trackers, and high- bandwidth pointing control systems which are critical for realizing future space-based astrometric and imaging interferometers.