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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2007

Conceptual Design of the TPF-O SC Bus

One option under current study for the Terrestrial Planet Finder-Occulter (TPF-O) observatory shares some key features of the Hubble Space Telescope (HST). Both are space telescopes with a primary mirror aperture of around 2.4 meters and designed to observe in the visible to near infrared range of wavelengths, with the major difference in science capability being that TPF-O has an areal FOV on the order of 100 times larger than that of HST. This larger FOV, whose science camera is also expected to provide fine guidance, and other mission differences, mean that most TPF-O SC bus subsystems will have very different requirements than those of HST. Unlike HST in LEO, TPF-O is designed to operate in an orbit around the Sun-Earth lagrange 2 (SEL2) point. The longer communications range to SEL2 and the large FOV require much higher performance data processing and communications than HST. Maintaining a SEL2 orbit requires TPF-O, unlike HST, to have a propulsion system. TPF-O will have a specialized tracking system that allows the formation flying occulter to maintain its required position. However, despite these additional features, the velocity required for reaching SEL2 and the limited capabilities of affordable launch vehicles require TPF-O to have a compact and low-mass design relative to HST. Finally, TPF-O may utilize a modular design to reduce development cost and, if it required, allow servicing using approaches different from those of HST.

Purves, Lloyd R.↗
NASA NTRS2007

Conceptual Design of the TPF-O SC Buses

The Terrestrial Planet Finder - Occulter (TPF-O) mission has two Spacecraft (SC) buses, one for a space telescope and the other for a formation-flying occulter. SC buses typically supply the utilities (support structures, propulsion, attitude control, power, communications, etc) required by the payloads. Unique requirements for the occulter SC bus are to provide the large delta V required for the slewing maneuvers of the occulter, and comunications for formation flying. The TPF-O telescope SC bus shares some key features of the one for the Hubble Space Telescope (HST): both support space telescopes designed to observe in the visible to near infrared range of wavelengths with comparable primary mirror apertures (2.4 m for HST, 2.4 - 4.0 m for TPF-O). However, TPF-O is expected to have a Wide Field Camera (WFC) with a Field of View (FOV) much larger than that of HST. Ths WFC is also expected to provide fine guidance. TPF-O is designed to operate in an orbit around the Sun-Earth Lagrange 2 (SEL2) point. The longer communications range to SEL2 and the large science FOV require higher performance communications than HST. Maintaining a SEL2 orbit requires TPF-O, unlike HST, to have a propulsion system. The velocity required for reachng SEL2 and the limited capabilities of affordable launch vehicles require both TPF-O elements to have compact, low-mass designs. Finally, it is possible that TPF-O may utilize a modular design derived fiom that of HST to allow servicing in the SEL2 orbit.

Purves, Lloyd R.↗
NASA NTRS2006

General Astrophysics with TPF: Not Just Dark Energy

Besides searching for Earth-LIke Planets, TPF can study Jupiters, Neptunes, and all sorts of exotic planets. It can image debris-disks, YSO disks, AGN disks, maybe even AGB disks. And you are probably aware that a large optical space telescope like TPF-C or TPF-O can be a fantastic tool for studying the equation of state of the Dark Energy. I will review some of the future science of TPF-C, TPF-I and TPF-O, focusing on the applications of TPF to the study of objects in our Galaxy: especially circumstellar disks and planets other than exo-Earths.

Kuchner, Marc↗
NASA NTRS2001

The TPF Mission at L2

The Terrestrial Planet Finder (TPF) is one of the center pieces of NASA's Origins Program. The goal of TPF is to identify terrestrial planets around stars nearby the Sun. For this purpose, a space-based interferometer with a baseline of approximately 100 m is required. To achieve such a large baseline, a distributed system of five spacecraft flying in formation is an efficient approach. Since the TPF instruments need a cold and stable environment, a halo orbit about 4 is ideal. First, we describe formation flight near the Lagrange point is feasible for the TPF mission. Second, we propose a novel approach for human servicing of Lagrange point missions by placing a Lunar service station in an Lunar L1 orbit. The TPF spacecraft can be transferred to a Lunar L1 orbit in a few days and requires relatively little delta-V. This efficient transfer results from the system of low energy pathways connecting the entire Solar System generated by the Lagrange points. The halo orbits are the portals of this Interplanetary . A Lunar Station at the L,portal, in addition to servicing missions from the Sun-Earth Lagrange points, may play an even more important role in the future development of space.

human servicing↗
NASA NTRS2006

TPF-C: Status and Recent Progress

The Terrestrial Planet Finder Coronagraph (TPF-C) is a deep space mission designed to detect and characterize Earth-like planets around nearby stars. TPF-C will be able to search for signs of life on these planets. TPF-C will use spectroscopy to measure basic properties including the presence of water or oxygen in the atmosphere; powerful signatures in the search for habitable worlds. This capability to characterize planets is what allows TPF-C to transcend other astronomy projects and become an historical endeavor on a par with the discovery voyages of the great navigators.

Terrestrial Planet Finder Coronagraph (TPF-C)↗
NASA NTRS2004

Formation acquisition sensor for the Terrestrial Planet Finder (TPF) mission

The Terrestrial Planet Finder (TPF) pre-project, an element of NASA’s Origins Program, is currently investigating multiple implementation architectures for finding earth-like planets around other stars. One of the technologies being developed is the Formation Flying Interferometer (FFI). The FFI is envisioned to consist of up to seven spacecraft, each with an infrared telescope, flying in precise formation within +/- l cm of pre-determined trajectories for synchronized observations. The spacecraft to- spacecraft separations are variable between 20 m to 100m during observations to support various interferometer configurations in the planet-finding mode. The challenges involved with TPF autonomous operations, ranging from formation acquisition and formation maneuvering, to high precision formation flying during science observations are unprecedented for deep space missions. To meet these challenges, the Formation Sensor Testbed (FST) under the TPF technology program will develop and demonstrate the key technology of the formation acquisition sensor. Key performance targets for the acquisition sensor are an instantaneous 4phi-steradian field of view and simultaneous range and bearing-angle measurements for multiple spacecraft with accuracy better than 50 cm and 1 degree, respectively. In this paper, we will describe the TPF FFI mission concept, the key formation flying challenges, the acquisition sensor design, the key design challenges, and the current plan to mitigate these design challenges.

Purcell, George H. Jr.↗
NASA NTRS2006

Progress in testing exo-planet signal extraction on the TPF-I Planet Detection Testbed

The TPF Interferometer (TPF-I) concept is being studied at the Jet Propulsion Laboratory and the TPF-I Planet Detection Testbed has been developed to simulate the detection process for an earthlike planet orbiting a star within about 15 pc. The testbed combines four beams of infrared light simulating the operation of a dual chopped Bracewell interferometer observing a star and a faint planet. This paper describes the results obtained this year including nulling of the starlight on four input beams at contrast ratios up to 250,000 to 1, and detection of faint planet signals at contrast ratios with the star of 2 million to 1.

nulling↗
NASA NTRS2007

Mission Studies for the Terrestrial Planet Finder - Occulter (TPF-O)

The 2000 decadal survey committee recommended a planet-finding telescope (TPF) capable of detecting and characterizing terrestrial planets orbiting nearby stars and of carrying out "revolutionary" astrophysics research. In response, we have carried out mission studies for TPF-O, a promising version of TPF that makes use of a "regular" telescope plus a free-flying occulter that blocks light from the target star while leaving planet light unattenuated. Our mission studies include design reference missions to carry out both planetary and general-astrophysics research. We will report on the results of these studies and describe their implications for the flight system and ground system.

Heap, S.↗
NASA NTRS2006

Status of the Terrestrial Planet Finder Interferometer (TPF-I)

The interferometric version of the Terrestrial Planet Finder (TPF-I) has the potential to find and characterize earth-sized planets in the habitable zones of over 250 nearby stars and to search for life using biomarkers in the atmospheres of any planets found. The scientific case for such a mission continues to be strengthened by on-going progress in the detection of planets via indirect means. This paper summarizes the status of TPF-I, illustrative scientific requirements for the mission, and its enabling technologies.

Terrestrial Planet Finder (TPF)↗
NASA NTRS2006

A Nulling Coronagraph for TPF-C

The nulling coronagraph is one of 5 instrument concepts selected by NASA for study for potential use in the TPF-C mission. This concept for extreme starlight suppression has two major components, a nulling interferometer to suppress the starlight to ~10(sup -10) per airy spot within 2 (lamda)/D of the star, and a calibration interferometer to measure the residual scattered starlight. The ability to work at 2 (lamda)/D dramatically improves the science throughput of a space based coronagraph like TPF-C. The calibration interferometer is an equally important part of the starlight suppression system. It measures the measures the wavefront of the scattered starlight with very high SNR, to 0.05nm in less than 5 minutes on a 5mag star. In addition, the post coronagraph wavefront sensor will be used to measure the residual scattered light after the coronagraph and subtract it in post processing to 1~2x10(sup -11) to enable detection of an Earthlike planet with a SNR of 5~10.

Terrestrial Planet Finder Coronagraph (TPF-C)↗
NASA NTRS2001

Simulation of formation flight near Lagrange points for the TPF Mission

In this paper, we focus on an orbit near the L***2***. Lagrange point. Our work in the study of the feasibility of formation flight near the Lagrange points indicates that 1) formation flight near L***2*** is dynamically possible for the TPF Mission and 2) linear control around a nonlinear baseline libration orbit near L***2*** is adequate for the TPF Mission.

TPF↗
NASA NTRS2001

Simulation of formation flight near Lagrange Points for the TPF Mission

The formation flight problem near the Lagrange points is of great interest. Recent work in the study of the feasibility of formation flight near the Lagrange points indicates that 1.) Formation flight near L2 is dynamically possible for the TPF Mission; and 2. Linear control around a nonlinear baseline libration orbit near L2 is adequate for the TPF Mission. This paper provides simulations which validate these conclusions.

TPF↗
NASA NTRS2004

TPF Minimum Mission Review

The Terrestrial Planet Finder (TPF) is a complex astronomical observatory requiring unprecedented optical accuracies and stabilities. I will present a preliminary outline of tests that will be required to establish the capability of TPF to detect terrestrial planets.

Smith, Andrew M.↗
NASA NTRS2007

TPF-I Emma X-Array: 2007 Design Team Study

This viewgraph presentation is a study of an Emma design for Terrestrial Planet Finder (TPF) formation flying interferometer. The objective is to develop a design with reduced cost compared to TPF-I X-Array, derive mass and cost estimates, and study thermal and radiation issues.

formation flying↗
NASA NTRS2006

Testing the TPF Interferometry Approach before Launch

One way to directly detect nearby extra-solar planets is via their thermal infrared emission, and with this goal in mind, both NASA and ESA are investigating cryogenic infrared interferometers. Common to both agencies' approaches to faint off-axis source detection near bright stars is the use of a rotating nulling interferometer, such as the Terrestrial Planet Finder interferometer (TPF-I), or Darwin. In this approach, the central star is nulled, while the emission from off-axis sources is transmitted and modulated by the rotation of the off-axis fringes. Because of the high contrasts involved, and the novelty of the measurement technique, it is essential to gain experience with this technique before launch. Here we describe a simple ground-based experiment that can test the essential aspects of the TPF signal measurement and image reconstruction approaches by generating a rotating interferometric baseline within the pupil of a large singleaperture telescope. This approach can mimic potential space-based interferometric configurations, and allow the extraction of signals from off-axis sources using the same algorithms proposed for the space-based missions. This approach should thus allow for testing of the applicability of proposed signal extraction algorithms for the detection of single and multiple near-neighbor companions...

interferometry↗
NASA NTRS2003

Pupil configurations for an interferometric TPF mission

The primary goal of the proposed Terrestrial Planet Finder mission is the direct detection of radiation from potential terrestrial planets orbiting around nearby stars. However, the faintness of the expected signals leads to very stringent technical requirements on the optical performance. As a result, both of the candidate approaches currently under active development by the TPF project, infrared nulling interferometry with separated aperture telescopes, and optical coronagraphy with a large singl aperture telescope, require complex optical systems which push the state of the art.

TPF interferometry Terrestrial Planet Finder↗
NASA NTRS2005

Study on the Station Keeping Maintenance for the TPF Mission

The main goal of this paper is to extend the results of Gomez et al, 2001, related to the execution of the formation manoeuvres of the TPF constellation, including the controls for the station keeping and allowing a greater flexibility in the basic manoeuvres to be done by the formation.

terrestrial planet finder (TPF)↗
NASA NTRS2007

Effects of Optical-density and Phase Dispersion of an Imperfect Band-limited Occulting Mask on the Broadband Performance of a TPF Coronagraph

Practical image-plane occulting masks required by high-contrast imaging systems such as the TPF-Coronagraph introduce phase errors into the transmitting beam., or, equivalently, diffracts the residual starlight into the area of the final image plane used for detecting exo-planets. Our group at JPL has recently proposed spatially Profiled metal masks that can be designed to have zero parasitic phase at the center wavelength of the incoming broadband light with small amounts of' 00 and phase dispersions at other wavelengths. Work is currently underway to design. fabricate and characterize such image-plane masks. In order to gain some understanding on the behaviors of these new imperfect band-limited occulting masks and clarify how such masks utilizing different metals or alloys compare with each other, we carried out some modeling and simulations on the contrast performance of the high-contrast imaging testbed (HCIT) at .JPL. In this paper we describe the details of our simulations and present our results.

integrated modeling↗