Abstract
We present a measurement of the Hubble constant
H
0
from surface brightness fluctuation (SBF) distances for 63 bright, mainly early-type galaxies out to 100 Mpc observed with the WFC3/IR on ...the Hubble Space Telescope (HST). The sample is drawn from several independent HST imaging programs using the F110W bandpass, with the majority of the galaxies being selected from the MASSIVE survey. The distances reach the Hubble flow with a median statistical uncertainty per measurement of 4%. We construct the Hubble diagram with these IR SBF distances and constrain
H
0
using four different treatments of the galaxy velocities. For the SBF zero-point calibration, we use both the existing tie to Cepheid variables, updated for consistency with the latest determination of the distance to the Large Magellanic Cloud from detached eclipsing binaries, and a new tie to the tip of the red giant branch (TRGB) calibrated from the maser distance to NGC 4258. These two SBF calibrations are consistent with each other and with theoretical predictions from stellar population models. From a weighted average of the Cepheid and TRGB calibrations, we derive
H
0
= 73.3 ± 0.7 ± 2.4 km s
−1
Mpc
−1
, where the error bars reflect the statistical and systematic uncertainties. This result accords well with recent measurements of
H
0
from Type Ia supernovae, time delays in multiply lensed quasars, and water masers. The systematic uncertainty could be reduced to below 2% by calibrating the SBF method with precision TRGB distances for a statistical sample of massive early-type galaxies out to the Virgo cluster measured with the James Webb Space Telescope.
Space radiation is one of the main concerns in planning long‐term human space missions. There are two main types of hazardous radiation: solar energetic particles (SEP) and galactic cosmic rays ...(GCR). The intensity and evolution of both depends on solar activity. GCR activity is most enhanced during solar minimum and lowest during solar maximum. The reduction of GCRs is alagging behind solar activity only by 6–12 month. SEP probability and intensity are maximized during solar maximum and are minimized during solar minimum. In this study, we combine models of the particle environment arising due to SEP and GCR with Monte Carlo simulations of radiation propagation inside a spacecraft and phantom. We include 28 fully ionized GCR elements from hydrogen to nickel and consider protons and nine ion species to model the SEP irradiation. Our calculations demonstrate that the optimal time for a flight to Mars would be launching the mission at solar maximum, and that the flight duration should not exceed approximately 4 years.
Plain Language Summary
Space particle radiation is one of the main concerns in planning long‐term human space missions. There are two main types of hazardous particle radiation: (a) solar energetic particles (SEP) originating from the Sun and (b) galactic cosmic rays (GCR) that come from the distant galaxies in space. Fluxes in particles of solar origin maximize during solar maximum when particles originating from the distant galaxies are more efficiently deflected from the solar system during times when the sun is active. Our calculations clearly demonstrate that the best time for launching a human space flight to Mars is during the solar maximum, as it is possible to shield from SEP particles. Our simulations show that an increase in shielding creates an increase in secondary radiation produced by the most energetic GCR, which results in a higher dose, introducing a limit to a mission duration. We estimate that a potential mission to Mars should not exceed approximately 4 years. This study shows that while space radiation imposes strict limitations and presents technological difficulties for the human mission to Mars, such a mission is still viable.
Key Points
Space missions to Mars should be scheduled to be launched during solar max
Optimal spacecraft shielding is ~30 g/cm2, which allows long‐duration flights of ~4 years
Increase of shielding thickness beyond ~30 g/cm2 results in dose increase
NASA has been tasked with implementing a bold vision of the future for human spaceflight including expanding the commercial market and operations in low-Earth orbit (LEO); launching the world's most ...powerful rocket and deep space crew spacecraft; incrementally establishing a sustainable presence on and around the Moon, starting by landing the first woman and the next man on the surface in 2024 while, in parallel, constructing an orbital Gateway in cislunar space. The key piece of establishing a sustainable presence in deep space is the development of habitation systems that will not only extend mission operations, but provide for living quarters that will keep the crew happy and healthy throughout their expeditions. Beyond the Gateway habitation needs, these capabilities will need to be defined and advanced to support the initial lunar surface missions and to prepare for human missions to the Mars system. The Foundation Surface Habitat (FSH) is the current concept in consideration to serve as this initial surface habitat that will extend the crew mission durations. It will provide 30-60 day habitability for a crew of four allowing for the astronauts to explore farther and longer on each visit to the lunar surface. The Transit Habitat is the current concept under study that would be capable of supporting long-duration missions. These missions could include extended operations at the Gateway or as a free-flyer facility in low-Earth orbit but ultimately, the Transit Habitat is envisioned as the crew habitat that would transport humans on long-duration deep space missions. The Transit Habitat integrated with an advanced propulsion system would serve as the in-space transportation system tasked with safely ferrying humans to and from Mars. Each of these habitation concepts is currently under study internal to NASA, but the agency is also working closely with U.S. industry through the Next Space Technologies for Exploration Partnerships (NextSTEP) activity to understand their concepts for a commercially-provided FSH and Transit Habitat as well as close coordination with our international partners to understand their desires for in-space and surface habitation. This paper will provide a status of these concepts and partnership activities as well as potential future development paths and architecture plans.
ABSTRACT We present a consistent optimal estimation retrieval analysis of 10 hot Jupiter exoplanets, each with transmission spectral data spanning the visible to near-infrared wavelength range. Using ...the NEMESIS radiative transfer and retrieval tool, we calculate a range of possible atmospheric states for WASP-6b, WASP-12b, WASP-17b, WASP-19b, WASP-31b, WASP-39b, HD 189733b, HD 209458b, HAT-P-1b, and HAT-P-12b. We find that the spectra of all 10 planets are consistent with the presence of some atmospheric aerosol; WASP-6b, WASP-12b, WASP-17b, WASP-19b, HD 189733b, and HAT-P-12b are all fit best by Rayleigh scattering aerosols, whereas WASP-31b, WASP-39b and HD 209458b are better represented by a gray cloud model. HAT-P-1b has solutions that fall into both categories. WASP-6b, HAT-P-12b, HD 189733b, and WASP-12b must have aerosol extending to low atmospheric pressures (below 0.1 mbar). In general, planets with equilibrium temperatures between 1300 and 1700 K are best represented by deeper, gray cloud layers, whereas cooler or hotter planets are better fit using high Rayleigh scattering aerosol. We find little evidence for the presence of molecular absorbers other than H2O. Retrieval methods can provide a consistent picture across a range of hot Jupiter atmospheres with existing data, and will be a powerful tool for the interpretation of James Webb Space Telescope observations.
Recent work suggests that strong emission line, star-forming galaxies (SFGs) may be significant Lyman continuum leakers. We combine archival Hubble Space Telescope broadband ultraviolet and optical ...imaging (F275W and F606W, respectively) with emission line catalogs derived from WFC3 IR G141 grism spectroscopy to search for escaping Lyman continuum (LyC) emission from homogeneously selected z ∼ 2.5 SFGs. We detect no escaping Lyman continuum from SFGs selected on O ii nebular emission (N = 208) and, within a narrow redshift range, on O iii/O ii. We measure 1 upper limits to the LyC escape fraction relative to the non-ionizing UV continuum from O ii emitters, fesc 5.6%, and strong O iii/O ii > 5 ELGs, fesc 14.0%. Our observations are not deep enough to detect fesc ∼ 10% typical of low-redshift Lyman continuum emitters. However, we find that this population represents a small fraction of the star-forming galaxy population at z ∼ 2. Thus, unless the number of extreme emission line galaxies grows substantially to z 6, such galaxies may be insufficient for reionization. Deeper survey data in the rest-frame ionizing UV will be necessary to determine whether strong line ratios could be useful for pre-selecting LyC leakers at high redshift.
Exploration analog field tests, missions, and deployments enable the integration and validation of new and experimental concepts and/or technologies through strategic experimental design. The results ...of these operations often create new capabilities for exploration and increase confidence in, and credibility of, emerging technologies, usually at very low cost and risk to the test subjects involved. While these experiments resemble missions 10-30 years into the future, insights obtained are often of immediate value. Knowledge gained in the field translates into strategic planning data to assist long-range exploration planners, and planners influence the experimental design of field deployments, creating a synergistic relationship. The Biologic Analog Science Associated with Lava Terrains (BASALT) communication architecture is a high-fidelity analog program that emulates conditions impacting future explorers on the martian surface. This article provides (1) a brief historical review of past analog operations that deliberately used elements of a flight-like telecommunication infrastructure to add fidelity to the test, (2) samples of the accomplishments made through analog operations, and (3) potentially significant deep-space telecommunication insights gained from the BASALT program in support of future extravehicular activity exploration of Mars. This article is paired with and complements Miller et al. in this issue which focuses on the telecommunication infrastructure utilized by the BASALT team during the field deployment.
We present the calibration and background model for the Large Area X-ray Proportional Counter (LAXPC) detectors on board AstroSat. The LAXPC instrument has three nominally identical detectors to ...achieve a large collecting area. These detectors are independent of each other, and in the event analysis mode they record the arrival time and energy of each photon that is detected. The detectors have a time resolution of 10 s and a dead-time of about 42 s. This makes LAXPC ideal for timing studies. The energy resolution and peak channel-to-energy mapping were obtained from calibration on the ground using radioactive sources coupled with GEANT4 simulations of the detectors. The response matrix was further refined from observations of the Crab after launch. At around 20 keV the energy resolution of the detectors is 10%-15%, while the combined effective area of the three detectors is about 6000 cm2.
Quantum computing experiments are moving into a new realm of increasing size and complexity, with the short-term goal of demonstrating an advantage over classical computers. Boson sampling is a ...promising platform for such a goal; however, the number of detected single photons is up to five so far, limiting these small-scale implementations to a proof-of-principle stage. Here, we develop solid-state sources of highly efficient, pure, and indistinguishable single photons and 3D integration of ultralow-loss optical circuits. We perform experiments with 20 pure single photons fed into a 60-mode interferometer. In the output, we detect up to 14 photons and sample over Hilbert spaces with a size up to 3.7 × 1014, over 10 orders of magnitude larger than all previous experiments, which for the first time enters into a genuine sampling regime where it becomes impossible to exhaust all possible output combinations. The results are validated against distinguishable samplers and uniform samplers with a confidence level of 99.9%.
Recently, with the rapid development of aerospace technology, an increasing number of spacecraft is being launched into space. Additionally, the demands for on-orbit servicing (OOS) missions are ...rapidly increasing. Space robotics is one of the most promising approaches for various OOS missions; thus, research on space robotics technologies for OOS has attracted increased attention from space agencies and universities worldwide. In this paper, we review the structures, ground verification, and on-orbit kinematics calibration technologies of space robotic systems for OOS. First, we systematically summarize the development of space robotic systems and OOS programs based on space robotics. Then, according to the structures and applications, these systems are divided into three categories: large space manipulators, humanoid space robots, and small space manipulators. According to the capture mechanisms adopted, the end-effectors are systematically analyzed. Furthermore, the ground verification facilities used to simulate a microgravity environment are summarized and compared. Additionally, the on-orbit kinematics calibration technologies are discussed and analyzed compared with the kinematics calibration technologies of industrial manipulators with regard to four aspects. Finally, the development trends of the structures, verification, and calibration technologies are discussed to extend this review work.
CCDLAB was originally developed as a FITS image data reducer and viewer, and development was then continued to provide ground support for the development of the UVIT detector system provided by the ...Canadian Space Agency to the Indian Space Research Organization's ASTROSAT satellite and UVIT telescopes. After the launch of ASTROSAT and during UVIT's first-light and PV phase starting in 2015 December, necessity required the development of a data pipeline to produce scientific images out of the Level 1 format data produced for UVIT by ISRO. Given the previous development of CCDLAB for UVIT ground support, the author provided a pipeline for the new Level 1 format data to be run through CCDLAB with the additional satellite-dependent reduction operations required to produce scientific data. Features of the pipeline are discussed with focus on the relevant data-reduction challenges intrinsic to UVIT data.
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