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At least 577 records · Page 32

An end-to-end data system for the Gamma-Ray Observatory

A data system, which includes parts in the orbiting Gamma-Ray Observatory and in its associated ground system, has been designed to rapidly deliver autonomous, packeted data to the science users. Data autonomy means all of the data, including auxiliary data, necessary for processing is included in the data packet that leaves the spacecraft. The data packets leaving the spacecraft remain unopened until they reach the user. Handling the data on a packet rather than a byte level allows simpler and generic software. The data goes through the system more quickly. This in turn reduces cost.

Hrastar, J.↗

The extreme ultraviolet imaging telescope on board SOHO

The design of the multibandpass Extreme-Ultraviolet Imaging Telescope designed for 1996 launch on board the Solar Heliospheric Observatory is described. The telescope will observe simultaneously distinct temperature ranges in the solar corona, defined by well chosen emission lines. Images in four narrow bandpasses at wavelengths ranging from 17 to 31 nm will be obtained using normal-incidence multilayered optics deposited on quadrants of a Ritchey-Chretien telescope. Results are presented on the performances measured on a 2/3 scale mock-up. The bandpasses could be adjusted to better than 1 percent in wavelength.

Delaboudiniere, J. P.↗

IAL SPACE: A test laboratory for the ISO cryogenic payload

The ESA Infrared Space Observatory (ISO) satellite is a 3 axes pointed platform designed to make accurate pointed observations of astronomical objects and sources in the wavelength range between 2.5 and 200 microns. ISO is composed of a service module and a payload module which is a large cylindrical vacuum vessel. The vessel is in fact a cryostat (capacity of 2250 l of liquid He II) which contains the telescope and the four focal scientific instruments. The latter being cooled up to a temperature less than 4 K. The qualification of the payload requires the measurement respectively of: the image quality of the telescope through wave front error (WFE) measurements; and the optical alignment of the scientific instruments with respect to the telescope axis and the telescope focus, and this under cryogenic conditions. Consequently, since 1988, the FOCAL 5 IAL Space facility has been upgraded in order to perform the cryogenic optical tests of the ISO optical subsystems.

Cucchiaro, A.↗

Status of the MACRO experiment at Gran Sasso

The design of the MACRO (Monopole Astrophysics and Cosmic Ray Observatory) experiment is described, and the results achieved by the running of its first supermodule are summarized. Searches for magnetic monopoles and point sources of downward muons resulted in no detections. One upward moving muon was seen along with abundant data on muon bundles.

Ahlen, Steve↗

Cosmology with liquid mirror telescopes

Liquid mirrors provide an exciting means to obtain large optical telescopes for substantially lower costs than conventional technologies. The liquid mirror concept has been demonstrated in the lab with the construction of a diffraction limited 1.5 m mirror. The mirror surface, using liquid mercury, forms a perfect parabolic shape when the mirror cell is rotated at a uniform velocity. A liquid mirror must be able to support a heavy mercury load with minimal flexure and have a fundamental resonant frequency that is as high as possible, to suppress the amplitude of surface waves caused by small vibrations transmitted to the mirror. To minimize the transmission of vibrations to the liquid surface, the entire mirror rests on an air bearing. This necessitates the mirror cell being lightweight, due to the limited load capabilities of the air bearing. The mirror components must also have physical characteristics which minimize the effects of thermal expansion with ambient temperature fluctuations in the observatory. In addition, the 2.7 m mirror construction is designed so that the techniques used may be readily extended to the construction of large mirrors. To attain the goals of a lightweight, rigid mirror, a composite laminant construction was used. The mirror consists of a foam core cut to the desired parabolic shape, with an accuracy of a few mm. An aluminum hub serves as an anchor for the foam and skin, and allows precise centering of the mirror on the air bearing and drive system. Several plys of Kevlar, covered in an epoxy matrix, are then applied to the foam. A final layer of pure epoxy is formed by spin casting. This final layer is parabolic to within a fraction of a mm. An aluminum ring bonded to the circumference of the mirror retains the mercury, and incorporates stainless-steel hard-points for the attachment of balance weights.

Hogg, David W.↗

High Resolution X-Ray Explorer (HIREX)

SAO has carried out a study to determine the feasibility of building an orbiting telescope capable of resolving 7 km structure on the Sun. In order to achieve the required imaging the telescope must have a resolution 0.01 arcsec. This fact challenges the state of the art of orbiting telescopes in several areas: mirror figuring; optical metrology; optical mounting; mirror figure control; system alignment; optical stability; observatory pointing; and image stability image stability. The telescope design concept is based on a 0.6m Cassegrain-style telescope with a 240 meter effective focal length. This is achieved with 2 mirrors supported at opposite ends of a 27 m space-deployable boom. The telescope mirrors are coated with multilayers designed to reflect a broad XUV passband. A third, small mirror, near the focal plane performs the function of selecting the narrow band that is finally imaged. Image stabilization to the 0.005 a,rcsec level is achieved by active control of the secondary mirror. The primary mirror is held unadjustably to the spacecraft, its pointing set by the space- craft orientation. The secondary mirror is mounted on a 6-axis stage that permits its position to be changed to align the telescope in space. The stage is intended for intermittent adjustment, both because of its speed of travel, and the TBD alignment procedure. The third mirror is called the TXI (Tuneable X-ray Imager). It is mounted on a gimbal that permits it to be tipped over a 60 degree range, selecting between the individual wavelengths in the initial bandpass. It can also rotated completely out of the way to allow the full, broadband EUV flux to strike the focal plane.

Golub, Leon↗

Kronos: A Multiwavelength Observatory for Mapping Accretion-Driven Sources

Kronos is a multiwavelength observatory proposed as a NASA Medium Explorer. Kronos is designed to make use of the natural variability of accreting sources to create microarcsecond-resolution maps of the environments of supermassive black holes in active galaxies and stella-size black holes in binary systems and to characterize accretion processes in Galactic compact binaries. Kronos will obtain broad energy range spectroscopic data with co-aligned X-ray, ultraviolet, and optical spectrometers. The high-Earth orbit of Kronos enables well-sampled, high time-resolution observations, critical for the innovative and sophisticated methods that are used to understand the accretion flows, mass outflows, jets, and other phenomena found in accreting sources. By utilizing reverberation mapping analysis techniques, Kronos produces advanced high-resolution maps of unprecedented resolution of the extreme environment in the inner cores of active galaxies. Similarly, Doppler tomography and eclipse mapping techniques characterize and map Galactic binary systems, revealing the details of the physics of accretion processes in black hole, neutron star, and white dwarf binary systems. The Kronos instrument complement, sensitivity, and orbital environment make it suitable to aggressively address time variable phenomena in a wide range of astronomical objects from nearby flare stars to distant galaxies.

Peterson, Bradley M.↗

Verification of the Solar Dynamics Observatory High Gain Antenna Pointing Algorithm Using Flight Data

The Solar Dynamics Observatory (SDO), launched in 2010, is a NASA-designed spacecraft built to study the Sun. SDO has tight pointing requirements and instruments that are sensitive to spacecraft jitter. Two High Gain Antennas (HGAs) are used to continuously send science data to a dedicated ground station. Preflight analysis showed that jitter resulting from motion of the HGAs was a cause for concern. Three jitter mitigation techniques were developed and implemented to overcome effects of jitter from different sources. These mitigation techniques include: the random step delay, stagger stepping, and the No Step Request (NSR). During the commissioning phase of the mission, a jitter test was performed onboard the spacecraft, in which various sources of jitter were examined to determine their level of effect on the instruments. During the HGA portion of the test, the jitter amplitudes from the single step of a gimbal were examined, as well as the amplitudes due to the execution of various gimbal rates. The jitter levels were compared with the gimbal jitter allocations for each instrument. The decision was made to consider implementing two of the jitter mitigating techniques on board the spacecraft: stagger stepping and the NSR. Flight data with and without jitter mitigation enabled was examined, and it is shown in this paper that HGA tracking is not negatively impacted with the addition of the jitter mitigation techniques. Additionally, the individual gimbal steps were examined, and it was confirmed that the stagger stepping and NSRs worked as designed. An Image Quality Test was performed to determine the amount of cumulative jitter from the reaction wheels, HGAs, and instruments during various combinations of typical operations. The HGA-induced jitter on the instruments is well within the jitter requirement when the stagger step and NSR mitigation options are enabled.

Bourkland, Kristin L.↗

In-Space Structural Assembly: Applications and Technology

As NASA exploration moves beyond earth's orbit, the need exists for long duration space systems that are resilient to events that compromise safety and performance. Fortunately, technology advances in autonomy, robotic manipulators, and modular plug-and-play architectures over the past two decades have made in-space vehicle assembly and servicing possible at acceptable cost and risk. This study evaluates future space systems needed to support scientific observatories and human/robotic Mars exploration to assess key structural design considerations. The impact of in-space assembly is discussed to identify gaps in structural technology and opportunities for new vehicle designs to support NASA's future long duration missions.

Belvin, W. Keith↗

Essential SpaceWire Hardware Capabilities for a Robust Network

The Geostationary Operational Environmental Satellite R-Series Program (GOES-R) mission is a joint program between National Oceanic & Atmospheric Administration (NOAA) and National Aeronautics & Space Administration (NASA) Goddard Space Flight Center (GSFC). GOES-R project selected SpaceWire as the best solution to satisfy the desire for simple and flexible instrument to spacecraft command and telemetry communications. GOES-R development and integration is complete and the observatory is scheduled for launch October 2016. The spacecraft design was required to support redundant SpaceWire links for each instrument side, as well as to route the fewest number of connections through a Slip Ring Assembly necessary to support Solar pointing instruments. The final design utilized two different router designs. The SpaceWire standard alone does not ensure the most practical or reliable network. On GOES-R a few key hardware capabilities were identified that merit serious consideration for future designs. Primarily these capabilities address persistent port stalls and the prevention of receive buffer overflows. Workarounds were necessary to overcome shortcomings that could be avoided in future designs if they utilize the capabilities, discussed in this paper, above and beyond the requirements of the SpaceWire standard.

SpaceWire↗

The NEID Precision Radial Velocity Spectrometer: Port Adapter Overview, Requirements, and Test Plan

The NEID spectrometer is an optical (380-930 nm), fiber-fed, precision Doppler spectrometer currently in development for the WIYN 3.5 m telescope at Kitt Peak National Observatory as part of the NN-EXPLORE partnership. Designed to achieve a radial velocity precision of < 30 cm/s, NEID will be sensitive enough to detect terrestrial-mass exoplanets around low-mass stars. Light from the target stars is focused by the telescope to a bent Cassegrain port at the edge of the primary mirror mechanical support. The specialized NEID "Port Adapter" system is mounted at this bent Cassegrain port and is responsible for delivering the incident light from the telescope to the NEID fibers. In order to provide stable, high-quality images to the science instrument, the Port Adapter houses several sub-components designed to acquire the target stars, correct for atmospheric dispersion, stabilize the light onto the science fibers, and calibrate the spectrometer by injecting known wavelength sources such as a laser frequency comb. Here we provide an overview of the overall opto-mechanical design and system requirements of the Port Adapter. We also describe the development of system error budgets and testplans to meet those requirements.

Cassegrain port↗

Ideas on the NASA Senior Review and Mission Extension Process

Extended mission budgets fund a significant part of our community, particularly young scientists who in a relatively short time are exposed to a broad range of experiences and opportunities available in space science and other STEM fields. In particular, mission-funded science offers a relatively stable funding stream that enables meaningful mentoring efforts and interactions, including apprenticeships ranging from project management, to mission operations, to data processing and analysis, to hardware and software development, to STEM-related education and outreach. It moreover provides professional contacts that fuel diversity in mission leadership and in the science and technical workforce at-large. Last but not least, it sustains the scientific productivity of NASA’s missions, which constitute major national investments meriting their full exploitation. Budgets cuts, however, are exercising pressure on the science and operations of the extended mission fleet despite being only a small portion of the overall Division budget. The history of Heliophysics has demonstrated that maintaining the operation of missions beyond their prime phase invariably leads to a much deeper knowledge of the original mission science goals, together with new applications often not foreseen during their original design. Their operation as part of the Heliophysics System Observatory (HSO)---a coordinated, 1eliophysics, multipoint observing system of the heliosphere, is a prime example. Some of the first activities undertaken by the Parker Solar Probe and Solar Orbiter missions required recreating the larger context of their new observations by using the diversity of HSO mission capabilities. The marginal cost of maintaining this valuable, working science resource, in the form of both continuing high quality data access and expertise, is small compared to the cost of the original missions or of new missions to achieve similar objectives, making the operation of extended missions, the best “science per dollar” investment in Heliophysics. We argue that reducing both extended mission operations and science budgets will have a ripple effect across the community, including reducing employment and training opportunities for young scientists, to lowering the quality/impact of the Heliophysics Systems Observatory. Instead, we suggest that the proposal process for mission extension should be re-examined. We offer several ideas for reducing costs of extended missions toward maintaining science output and streamlining the management process.

A. Vourlidas↗

Design for a complete SOHO mission under the ISTP

The Solar and Heliospheric Observatory (SOHO) occupies a crucial slot in the International Solar Terrestrial Physics (ISTP) program, which investigates the energy and material flows in key regions of the geospace. Prior space missions which have brought understanding of the corona to what it is today are reviewed. Similarly, space science programs on the horizon will build on SOHO discoveries and insights. SOHO program structure and cost control methods are sketched; tasks have been transferred off the spacecraft where possible, and capabilities will be delivered just before needed. The team analyses of data will be augmented by a SOHO guest investigator program after launch. Theorists on teams would similarly be joined by participants in a proposed SOHO theory program. The ISTP program is built on a foundation of collaborative science, implying the need for observational campaigns directed from a user friendly operations center.

Wagner, W. J.↗

Testing and Calibration of the NASA COR1 Coronagraph for the Solar Terrestrial Relations Observatory (STEREO)

This proposal is for a no cost extension on the period of performance of the existing grant. The period of performance shall be extended to the end of FY 2003. This extension is required due to schedule changes in the COR1 program. Funding for Phase II and Phase III of this grant has been obtained. This unsolicited proposal was for scientific and engineering collaboration between NASA s Goddard Space Flight Center (GSFC) and HAO. Performance testing of the COR1 engineering test unit has been partially completed. The COR1 coronagraph engineering test unit requires further testing at NASA s GSFC and the National Center for Atmospheric Research (NCAR) Mauna Loa Solar Observatory (MLSO), operated by the High Altitude Observatory (HAO). HAO personnel have recently supported efforts to test component and breadboard versions of the COR1 using the NCAR Vacuum Tunnel Facility (NVTF). HAO personnel will continue to work closely with scientists and engineers at NASA/GSFC in the development, design, assembly, testing, and operation of this key element of NASA's Solar Terrestrial Relations Observatory (STEREO) mission. The element is an internally-occulted coronagraphic telescope, and the design and development effort is already underway at GSFC.

Burkepile, J. T.↗

Optical Alignment of the JWST ISIM to the OTE Simulator (OSIM): Current Concept and Design Studies

The James Webb Space Telescope's (JWST) Integrated Science Instrument Module (ISIM) contains the observatory's four science instruments and their support subsystems. During alignment and test of the integrated ISIM at NASA's Goddard Space Flight Center (GSFC), the Optical'telescope element SIMulator (OSIM) will be used to optically stimulate the science instruments to verify their operation and performance. In this paper we present the design of two cryogenic alignment fixtures that will be used to determine and verify the proper alignment of OSIM to ISIM during testing at GSFC. These fixtures, the Master Alignment Target Fixture (MAW) and the ISIM Alignment Target Fixture (IATF), will provide continuous, six degree of freedom feedback to OSIM during initial ambient alignment as well as during cryogenic vacuum testing. These fixtures will allow us to position the OSIM and maintain OSIM-ISIM alignment to better than 10 microns in translation and 250 micro-radians in rotation. We will provide a brief overview of the OSIM system and calibration and we will also discuss the relevance of these fixtures in the context of the overall ISIM alignment and verification plan.

Frey, Bradley J.↗

Photoheliograph thermal concepts study. Volume 1: Summary

The performances of thermal subsystem concepts for each of three photoheliograph designs oriented toward unique solar observation missions are defined. These designs and missions may be categorized as: (1) A 150-centimeter photoheliograph for large Solar Observatory (LSO) missions; (2) a 100-centimeter photoheliograph for shuttle sorties; and (3) a 100-centimeter photoheliograph for balloon missions. For each of these photoheliograph designs are the basic thermal environments, boundary conditions, and applicable thermal control concepts defined, the interactions between concepts and environments determined, and a baseline thermal control concept for the three classes of photoheliographs selected. A set of experimental work plans describing the major efforts required to further the detailed design and to confirm analytical performance predictions is included.

Source record↗

Thermal and cryogenic design study for space infrared telescope facility (SIRTF)

A study was conducted to determine the ability of an all superfluid helium design to meet the performance requirements of background limited to 200 micrometer, and a two year lifetime for a one meter class free flying infrared observatory. Both a 98 deg and 28.5 deg inclination orbits were examined, and aperture shade designs were developed for both orbits. A unique forebaffle cooling design significantly reduces the sensitivity to aperture heat loads. With certain restrictions on observing modes, the study determined that an all superfluid helium Dewar will meet the temperature and lifetime requirements. A dual cryogen SFHe/SH2 system was also investigated for the 28.5 deg orbit and found to provide a more constant forebaffle temperature but with only a slight improvement in lifetime.

Urbach, A. R.↗

Nancy Grace Roman Space Telescope Observatory Implementation and Challenges

NASA’s Nancy Grace Roman Space Telescope (Roman), previously referred to as Wide Field Infrared Survey Telescope (WFIRST), was named after Dr. Nancy Grace Roman, an astronomer and NASA pioneer of modern space-based astronomy who is known as the “mother of the Hubble Space Telescope”. Roman is a deep space infrared observatory with a Hubble-sized telescope and wide field of view instrument (greater than 100 times that of Hubble’s) that will conduct a high latitude time-domain survey, a high latitude imaging and spectroscopic survey, and a galactic bulge time-domain survey to characterize dark energy and expand the census of exoplanets in our galaxy while allowing a broad range of astrophysics research. Roman will also demonstrate exoplanet coronagraphy with active wave front control technology and provide general investigator programs for the science community. Roman is finishing the critical design phase and is planning for launch in 2026. It will operate in a quasi-halo orbit about Sun-Earth L2, 1.5 million kilometers from Earth, for a five-year primary mission life. The Observatory features an Optical Telescope Assembly with an existing, repurposed 2.4m primary mirror, a Wide Field Instrument with a focal plane array comprised of 18 HgCdTe near-infrared detectors and a grism, prism and filter elements for imaging and spectroscopy in support of the primary surveys, as well as a Coronagraph instrument technology demonstration with starlight suppression technology for direct imaging and spectroscopy of exoplanets. The telescope is mounted to the Instrument Carrier composite truss structure which also optically meters each instrument, includes a Launch Load and Vibration Isolation System to provide passive isolation of spacecraft jitter sources while also supporting the payload during launch and is attached to the Spacecraft Bus. The Spacecraft also includes a Solar Array Sunshield ,Deployable Aperture Cover, Lower Instrument Sunshade, High Gain Antenna System, and Outer Barrel Assembly. Figure 1 shows an overview of the Roman Observatory. When fully integrated, Roman will be the largest Observatory assembled and tested at NASA’s Goddard Space Flight Center. Figure 1. Roman Observatory Overview Development of scientific satellites is challenging by nature, as the pursuit to broaden scientific knowledge always pushes the boundary of what has come before. The implementation of the Roman mission is a prime example and expected challenges have been augmented by the foundational decision to use the existing telescope components, developed in the early 2000s by another Government agency for a different application. Other unique aspects of the Roman mission, such as its survey nature, the vast amount of data required to meet science objectives, and packaging of the Observatory elements around the existing telescope components, create constrained design spaces that drive competing requirements across Observatory subsystems. Given these challenges, systems engineering has been a critical discipline in balancing implementation decisions for the Roman mission and will continue to play a key role going forward. This paper will discuss details of the Roman Observatory configuration, as well as some of the systems engineering challenges and the decision-making process used to mature the Roman Space Telescope preliminary design to implementation.

Lisa Ml Bartusek↗