Exo-Planets and Stellar Astrophysics Lab

ExoPlanets & Stellar Astrophysics Programs/Missions

Current

Space Telescope Imaging Spectrograph (STIS)

Bruce Woodgate is the Principal investigator for the Space Telescope Imaging Spectrograph (STIS) currently onboard the Hubble Space Telescope. STIS provides medium and high spectral resolution imaging in the ultraviolet and visible wavelength bands. In addition to Deputy PI Ted Gull, Co-Is Chuck Bowers, Sally Heap and Randy Kimble are team members. Throughout its life, since installation on HST in 1997, STIS has observed the interstellar and intergalactic medium and made possible observations of the "transiting extra-solar planet" (HD 209458b). After suffering a power supply failure, STIS was recently repaired by the astronauts during the Hubble Servicing Mission 4.

Infrared Array Camera (IRAC)

IRAC is a camera onboard the Spitzer Space Telescope (aka SIRTF), a cryogenically cooled IR telescope and the last of the Great Observatories. M81

It was launched in August 2003, and is working as well or better than designed. The picture to the right is a true color (3.6, 4.5, 5.8, 8 micron) image of the galaxy M81 obtained with IRAC and released in December 2003 [image credit: NASA/JPL-Caltech/Willner (Harvard-Smithsonian Center for Astrophysics)]. IRAC was built at GSFC; Harvey Moseley is the Instrument Scientist. G. Fazio at Harvard is the P.I. IRAC contains 2 InSb arrays (1-5.5 microns), and 2 HgCdTe arrays (2- 28 microns).

Fizeau Interferometry Testbed (FIT)

An overview of the Phase I FIT, with baffles removed to show the optical elements clearly.

The Fizeau Interferometry Testbed is a ground-based experiment located in the GSFC Instrument Development Lab. It is a collaborative effort by K. Carpenter (PI), R. Lyon, and R. Barry at GSFC, D. Mozurkewich at Seabrook Engineering, and J. Marzouk, P. Petrone, P. Dogoda, and P. Liiva at Sigma Space Corporation. FIT is being used to develop and test algorithms for closed-loop optical control of actuated many-element sparse aperture systems, using feedback from analysis of the wavefront errors in the combined beams of science data - a critical technology for future long-baseline Fizeau Interferometers and Sparse Aperture Telescopes, such as the Stellar Imager (SI) mission. The FIT currently uses 7 articulated mirrors each having tip, tilt and piston that are automatically controlled to demonstrate closed-loop control and keep the beams phased to simulate a 7-element formation-flying interferometer. The number of elements will be increased to ~18 for FIT Phase II by the Fall of 2009, in order to bring the FIT design into closer agreement with that of actual large strategic missions like SI.

Wide Field Camera 3 (WFC3)

WFC3 was recently successfully installed on the Hubble Space Telescope by astronauts during Servicing Mission 4. This panchromatic camera offers imaging from 200nm to 1.7 microns. The Instrument Scientist is Randy Kimble. The characteristics of the CCDs and Rockwell HgCdTe IR arrays have been tested at GSFC in the Detector Characterization Lab, which is jointly operated by the ASD and the GSFC engineering directorate. The picture of WFC3 (right) was taken during assembly at Ball Aerospace.

Advanced Camera for Surveys (ACS)

The Advanced Camera for Surveys (ACS) is a third generation Hubble Space Telescope Instrument. The ACS was installed during HST servicing mission3B and repaired during servicing mission 4. The 3rd generation imager included three channels: the Wide Field Channel (WFC), the High Resolution Channel (HRC), and the Solar Blind Channel (SBC). The WFC was designed for efficient wide-area surveys at visible wavelengths. The HRC provided high angular resolution over a small field of view, covering a broad wavelength range. The SBC was designed for observing faint ultraviolet emission from sources bright at visible wavelengths. After installation, ACS became the most heavily used instrument on Hubble, and has led to a wide range of scientific discovery. GSFC Co-Is are Mark Clampin and Randy Kimble.

Future

Terrestrial Planet Finder (TPF)

The Terrestrial Planet Finder (TPF) is a series of two missions to detect and characterize earth-like planets around nearby stars. The TPF optical coronagraph (TPF-C) will be the first to fly, followed by an infrared interferometer (TPF-I) about five years later. The launch schedule is under review at present, with a TPF-C launch expected no earlier than about 2016. Goddard is collaborating on TPF with JPL, which is the lead Center for TPF. Goddard's primary role is to build the telescopes for TPF-C and TPF-I. In addition, scientists in the Exoplanet Lab are studying a number of technologies relevant to TPF (masks, visible nulling coronagraphy, interferometry, mirror coatings, and spectrographs). Sally Heap and Chuck Bowers are the Telescope and Deputy Telescope Scientists, respectively, for TPF-C. Bill Danchi is the Telescope Scientist for TPF-I, and is the TPF Project Liaison with ESA's Darwin Project. For further info, also visit JPL's TPF site.

Stellar Imager (SI)

An artist's concept of one possible Stellar Imager architecture K. Carpenter is leading the development of the Stellar Imager (SI), a UV-Optical, Space-Based Interferometer with over 200x the spatial resolution of HST. It is designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and, via spatially-resolved asteroseismology, stellar interiors and of the Universe in general. Its spectral imaging capability will enable an improved understanding of: 1) Solar/stellar dynamos and magnetic activity and their roles in the formation and evolution of stars and in the habitability of planets, 2) mass transport processes and their roles in the formation, structure, and evolution of stars and stellar systems, and 3) Active Galactic Nuclei (AGN) and their role in galaxy formation and evolution. SI is an implementation of the UV Optical Interferometer (UVOI) in the 2006 Astrophysics Strategic Plan and a Flagship "Landmark/Discovery Mission" in the 2005 Heliophysics Roadmap. It is a NASA Vision Mission ("NASA Space Science Vision Missions" (2008), ed. M. Allen) and has also been recommended for further study in an NRC Report (2008) on missions potentially enhanced by an Ares V launch, although the baseline mission design can be launched using existing EELV's (e.g. Delta IV H).

The ultra-sharp images of the Stellar Imager will revolutionize our view of many dynamic astrophysical processes: the 0.1 mas resolution of this deep-space telescope will transform point sources into extended sources, and snapshots into evolving views. SI's science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI's prime goal is to enable long-term forecasting of solar activity and the space weather that it drives in support of the "Living With a Star" program in the Exploration Era. SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes in the Universe. This "Vision Mission" concept is being developed by GSFC in collaboration with a broad variety of industrial, academic, and astronomical science institute partners, as well as an international group of science and technical advisors. Please see the Stellar Imager Homepage for further information.

EPIC (Extrasolar Planet Imaging Coronagraph)

M. Clampin is the Principal Investigator for EPIC, a Discovery Mission concept. EPIC is designed to directly image and characterize extrasolar gas giant planets (EGPs) at typical distances of 2 to 20 AU from the parent star, and will therefore find solar-system analogs - those most likely to harbor earth-like planets. Such systems will be the primary targets for NASA's subsequent planet searches with the Terrestrial Planet Finder (TPF). EPIC's direct planet discovery capabilities are complemented by its unique ability to image the dust disks and very low-mass companions close in to stars. The EPIC concept employs a visible nulling coronagraph and a 1.5-m aperture telescope. GSFC team members include Dan Gezari and Rick Lyon.

Fourier Kelvin Stellar Interferometer (FKSI)

W. Danchi is leading the development of the Fourier-Kelvin Stellar Interferometer (FKSI), with Drs. D. Benford, D. Leisawitz, D. Gezari, S. Rinehart, J. Rajagopal, D. Deming and M. Mumma at GSFC, together with numerous members of the community. FKSI is a mission concept for a nulling interferometer for the near to mid infrared spectral region (3-8 microns). FKSI is conceived as a scientific and technological precursor to the Terrestrial Planet Finder (TPF) mission. The scientific emphasis of the mission is on the evolution of protostellar systems, from just after the collapse of the precursor molecular cloud core, through the formation of the disk surrounding the protostar, the formation of planets in the disk, and eventual dispersal of the disk material. FKSI will address key questions about exosolar planets: (1) what are the characteristics of exosolar giant planets? (2) what are the characteristics of exosolar zodiacal clouds around nearby stars? and (3) are there giant planets around classes of stars other than those already studied? In the past year, a detailed design study for FKSI was undertaken at GSFC. Using a nulling interferometer configuration, the optical system consists of two 0.5m telescopes on a 12.5m boom feeding a Mach-Zender beam combiner with a fiber wavefront error reducer to produce a 0.01% null of the central starlight. With this system, planets around nearby stars can be detected and characterized using a combination of spectral and spatial resolution. For further information, check out this recent poster on FKSI from the ESO Garching conference (Oct 2005): PPT file.

James Webb Space Telescope (JWST) Development

ASD is home to the scientists developing JWST. John Mather is Senior Project Scientist, Jon Gardner is Deputy Senior Project Scientist, Mark Clampin is the Observatory Project Scientist, Matt Greenhouse is Project Scientist for the Integrated Science Instrument Module (ISIM), Bernie Rauscher is Deputy ISIM Project Scientist for detector development, and George Sonneborn is Operations Project Scientist. Programmable transmissive microshutter arrays are being developed using MEMS technology for the JWST Near Infrared Spectrograph (NIRSpec) by Moseley, Silverberg, Kutyrev, and Woodgate. Each shutter is individually controllable (open or closed). The transmissive design allows high contrast, compared to reflective micro- mirror approaches. To date, a 256x256 pixel array has been constructed and tested at cryogenic temperatures. Both the NIRCam (near-IR) and MIRI (mid-IR) cameras contain coronagraphs, and the study of debris disks and Extrasolar Giant Planets (EGPs) is one of the primary scientific goals of JWST.

Next Generation UV detectors

Woodgate, Kimble, Norton, Stock and Hilton are developing high QE detectors for use in the UV, based on new photocathode materials such as AlGaN for deposition on silicon-based microchannel plates. Recent results show improvements in Quantum Efficiency in the Near-UV (180 nm) to 55%, and in the Far-UV (122 nm) to 72%. Kimble, Norton, Haas and B. Pain (JPL) are developing an Active Pixel Sensor (APS) for eventual use in a UV camera together with the high QE microchannel plate. Tim Norton is shown at left in the detector processing lab in B21 at Goddard.