Review Report on the WFIRST

An independent review board for NASA’s next flagship astronomy mission concluded in its final report that the project is “not executable” without additional funding or adjustments to the spacecraft.

NASA released the report, a 65-page document in the form of a PowerPoint presentation, Nov. 22, a month after the agency published its response calling for a reduction in the proposed cost of the Wide-Field Infrared Survey Telescope (WFIRST) and changes to its management.

The report, prepared by an outside committee established by NASA called the WFIRST Independent External Technical/Management/Cost Review (WIETR), found that various changes made to WFIRST since it was proposed as the top-ranking large, or flagship, mission in the 2010 astrophysics decadal survey created cost and technical difficulties.

“After multiple discussions that set the boundary conditions, NASA HQ made a series of decisions that set the stage for an approach and mission system concept that is more complex than probably anticipated from the point of view of scope, complexity, and the concomitant risks of implementation,” the report stated.

link.

Space Technology for Directly Imaging and Characterizing Exo-Earths

Space Technology for Directly Imaging and Characterizing Exo-Earths

Authors:

Crill et al

Abstract:

The detection of Earth-like exoplanets in the habitable zone of their stars, and their spectroscopic characterization in a search for biosignatures, requires starlight suppression that exceeds the current best ground-based performance by orders of magnitude. The required planet/star brightness ratio of order 1e-10 at visible wavelengths can be obtained by blocking stellar photons with an occulter, either externally (a starshade) or internally (a coronagraph) to the telescope system, and managing diffracted starlight, so as to directly image the exoplanet in reected starlight. Coronagraph instruments require advancement in telescope aperture (either monolithic or segmented), aperture obscurations (obscured by secondary mirror and its support struts), and wavefront error sensitivity (e.g. line-of-sight jitter, telescope vibration, polarization). The starshade, which has never been used in a science application, benefits a mission by being decoupled from the telescope, allowing a loosening of telescope stability requirements. In doing so, it transfers the difficult technology from the telescope system to a large deployable structure (tens of meters to greater than 100 m in diameter) that must be positioned precisely at a distance of tens of thousands of kilometers from the telescope. We describe in this paper a roadmap to achieving the technological capability to search for biosignatures on an Earth-like exoplanet from a future space telescope. Two of these studies, HabEx and LUVOIR, include the direct imaging of Earth-sized habitable exoplanets as a central science theme.

NASA's Next Space Telescope (JWST) is Delayed

NASA announced Sept. 28 that the launch of the James Webb Space Telescope mission, which had been planned for next fall, will now be delayed until the spring of 2019.

In a statement posted on the agency’s website, NASA said that an assessment of overall work needed to complete integration and testing of the $8 billion spacecraft led to the decision to postpone the launch by about half a year.

“The change in launch timing is not indicative of hardware or technical performance concerns,” Thomas Zurbuchen, NASA associate administrator for science, said in the statement. “Rather, the integration of the various spacecraft elements is taking longer than expected.”

The release noted that testing of the telescope and its instruments “continues to go well and on schedule” in a thermal vacuum chamber at the Johnson Space Center but that the spacecraft bus and sunshield, being assembled at a Northrop Grumman facility in California, were suffering delays.

link.

Anomalies Detected in James Webb Telescope During Testing

Earlier this month, on Dec. 3, accelerometers at NASA’s Goddard Space Flight Center (GSFC) detected “anomalous readings” in a portion of the James Webb Space Telescope (JWST). These “readings” took place during vibration tests being conducted to simulate anticipated launch conditions.

link.

The James Webb Space Telescope..the trailer?

James Webb Space Telescope Mirror Tested

Engineers and technicians working on the James Webb Space Telescope successfully completed the first important optical measurement of Webb's fully assembled primary mirror, called a Center of Curvature test.

Taking a "before" optical measurement of the telescope's deployed mirror is crucial before the telescope goes into several stages of rigorous mechanical testing. These tests will simulate the violent sound and vibration environments the telescope will experience inside its rocket on its way out into space. This environment is one of the most stressful structurally and could alter the shape and alignment of Webb's primary mirror, which could degrade or, in the worst case, ruin its performance.

link.

There are Concerns About WFIRST's Cost Growing

The estimated cost of NASA’s next major astrophysics mission after the James Webb Space Telescope has increased by up to 25 percent, growth that a new report warns could hurt other priorities for NASA astronomy missions in the coming years.

The potential cost increase in the Wide Field Infrared Survey Telescope (WFIRST) mission was noted in a report issued by the National Academies Aug. 15 that reviewed the progress by NASA and other agencies in implementing the most recent astrophysics decadal survey, published in 2010.

WFIRST, which became a formal project in February, had an estimated cost of $2.0 to 2.3 billion, based on an independent cost and technical estimate performed by the Aerospace Corp. in 2015. However, the National Academies report said that between the completion of that assessment and the decision to make WFIRST a formal project, known as Key Decision Point A, the cost of the mission had increased by $550 million.

Part of that increase, according to the report, is linked to the decision to fly WFIRST at the Earth-sun L-2 Lagrange point, about 1.5 million kilometers from the Earth, rather than in geostationary orbit as originally planned. Increased prices for the baseline launch vehicle, a United Launch Alliance Delta 4 Heavy, also contributed to the cost growth by an unknown amount. “Some of it may simply reflect more accurate assessment as the mission design matures,” the report added.

NASA spokeswoman Felicia Chou said Aug. 15 that of that $550 million increase, only $100 million was linked to design changes to the WFIRST spacecraft. The rest, she said, was caused by factors that included a change in the estimated launch vehicle price and a delayed launch date.

link.

WFIRST's Evolution

Many NASA missions and projects have become household names – Apollo, Hubble, and, more recently, Curiosity. These names are chosen with care, and the names themselves can change over the course of a project, from inception to completion. Tracking the changing names of a project can reveal the story of a mission's development. NASA’s next big “flagship” astronomy mission, following the ambitious James Webb Space Telescope due to be launched in 2018, is currently known as the Wide Field Infrared Survey Telescope (WFIRST). When NASA formally committed to flying WFIRST in February 2016, news stories stated that NASA had then "begun" work on WFIRST. This amused me because I, along with many of my colleagues, had already put hundreds of collective work-years into the development of WFIRST, under a slew of different names.

link.

Oxygen Detected in beta Pictoris' Protoplanetary Disk

Herschel detects oxygen in the beta Pictoris debris disk

Authors:

Brandeker et al

Abstract:

The young star beta Pictoris is well known for its dusty debris disk, produced through the grinding down by collisions of planetesimals, kilometre-sized bodies in orbit around the star. In addition to dust, small amounts of gas are also known to orbit the star, likely the result from vaporisation of violently colliding dust grains. The disk is seen edge on and from previous absorption spectroscopy we know that the gas is very rich in carbon relative to other elements. The oxygen content has been more difficult to assess, however, with early estimates finding very little oxygen in the gas at a C/O ratio 20x higher than the cosmic value. A C/O ratio that high is difficult to explain and would have far-reaching consequences for planet formation. Here we report on observations by the far-infrared space telescope Herschel, using PACS, of emission lines from ionised carbon and neutral oxygen. The detected emission from C+ is consistent with that previously reported being observed by the HIFI instrument on Herschel, while the emission from O is hard to explain without assuming a higher-density region in the disk, perhaps in the shape of a clump or a dense torus, required to sufficiently excite the O atoms. A possible scenario is that the C/O gas is produced by the same process responsible for the CO clump recently observed by ALMA in the disk, and that the re-distribution of the gas takes longer than previously assumed. A more detailed estimate of the C/O ratio and the mass of O will have to await better constraints on the C/O gas spatial distribution.

WASP-157b: a Transiting Hot Jupiter Observed with K2

WASP-157b, a Transiting Hot Jupiter Observed with K2

Authors:

Močnik et al

Abstract:

We announce the discovery of the transiting hot Jupiter WASP-157b in a 3.95-d orbit around a V = 12.9 G2 main-sequence star. This moderately inflated planet has a Saturn-like density with a mass of 0.57±0.10 MJup and radius 1.04±0.04 RJup. The small projected stellar rotational velocity of 1.0±0.9 km s−1 suggests that the host star is a slow rotator or that the star rotates close to pole-on. We do not detect any rotational or phase-curve modulations, nor the secondary eclipse, with conservative semi-amplitude upper limits of 250 and 30 ppm, respectively.

On the Feasibility of Characterizing Free-floating Planets with Current and Future Space-based Microlensing Surveys

On the Feasibility of Characterizing Free-floating Planets with Current and Future Space-based Microlensing Surveys

Authors:

Henderson et al

Abstract:

Simultaneous space- and ground-based microlensing surveys, such as K2's Campaign 9 (K2C9) and WFIRST, facilitate measuring the masses and distances of free-floating planet (FFP) candidates. FFPs are identified as single-lens events with a short timescale, of-order 1 day. Measuring the mass of the lensing object requires determining the finite size of the source star ρ, as well as the microlens parallax πE. A planet that is bound to but widely separated from a host star can produce a light curve similar to that of an FFP. This tension can be resolved with high-resolution imaging of the microlensing target to search for the lens flux Fl from a possible host star. Here we investigate the accessible parameter space for each of these components --- πE, ρ, and Fl --- considering different satellites for a range of FFP masses, Galactic distances, and source star properties. We find that at the beginning of K2C9, when its projected separation from the Earth (as viewed from the center of its survey field) is ≲0.2 AU, it will be able to measure πE for Jupiter-mass FFP candidates at distances larger than ∼2 kpc and to Earth-mass lenses at ∼8 kpc. At the end of its campaign, when D⊥=0.81 AU, it is sensitive to planetary-mass lenses for distances ≳3.5 kpc, and even then only to those with mass ≳MJup. From lens flux constraints we find that it will be possible to exclude all stellar-mass host stars (down to the deuterium-burning limit) for events within ∼2 kpc. Together these indicate that the ability to characterize FFPs detected during K2C9 is optimized for events occurring toward the beginning of the campaign. WFIRST, on the other hand, will be able to detect and characterize FFPs with masses at least as low as super-Earths throughout the Galaxy during its entire microlensing survey.

EPIC210957318b & EPIC212110888b: An independent discovery of two hot Jupiters

An independent discovery of two hot Jupiters from the K2 mission

Authors:

Brahm et al

Abstract:

We report the discovery of two hot Jupiters using photometry from Campaigns 4 and 5 of the two-wheeled Kepler (K2) mission. EPIC210957318b has a mass of 0.65±0.14MJ, a radius of 1.070±0.018RJ and transits its G dwarf (Teff=5675±50 K), slightly metal rich ([Fe/H]=+0.06±0.04 dex) host star in a 4.1 days circular orbit. EPIC212110888b has a mass of 1.63±0.12MJ, a radius of 1.38±0.014RJ and has an orbital period of 3.0 days in which it orbits a late F dwarf (Teff=6149±55 K) solar metallicity star. Both planets were validated probabilistically and confirmed via precision radial velocity (RV) measurements. They have physical and orbital properties similar to the ones of the already uncovered population of hot Jupiters and are well-suited candidates for further orbital and atmospheric characterization via detailed follow-up observations.

James Webb Space Telescope Instruments Installed

With surgical precision, two dozen engineers and technicians successfully installed the package of science instruments of the James Webb Space Telescope into the telescope structure. The package is the collection of cameras and spectrographs that will record the light collected by Webb's giant golden mirror.

link.

K2-3 & K2-26 Systems Observed by Spitzer

Spitzer Observations of Exoplanets Discovered with The Kepler K2 Mission

Authors:

Beichman et al

Abstract:

We have used the Spitzer Space Telescope to observe two transiting planetary systems orbiting low mass stars discovered in the Kepler K2 mission. The system K2-3 (EPIC 201367065) hosts three planets while EPIC 202083828 (K2-26) hosts a single planet. Observations of all four objects in these two systems confirm and refine the orbital and physical parameters of the planets. The refined orbital information and more precise planet radii possible with Spitzer will be critical for future observations of these and other K2 targets. For K2-3b we find marginally significant evidence for a Transit Timing Variation between the K2 and Spitzer epochs.

One Proposed Early Science Effort for JWST Will be Observing hot Jupiter WASP-62b's Atmosphere

Transiting Exoplanet Studies and Community Targets for JWST's Early Release Science Program

Authors:

Stevenson et al

Abstract:

The James Webb Space Telescope will revolutionize transiting exoplanet atmospheric science due to its capability for continuous, long-duration observations and its larger collecting area, spectral coverage, and spectral resolution compared to existing space-based facilities. However, it is unclear precisely how well JWST will perform and which of its myriad instruments and observing modes will be best suited for transiting exoplanet studies. In this article, we describe a prefatory JWST Early Release Science (ERS) program that focuses on testing specific observing modes to quickly give the community the data and experience it needs to plan more efficient and successful future transiting exoplanet characterization programs. We propose a multi-pronged approach wherein one aspect of the program focuses on observing transits of a single target with all of the recommended observing modes to identify and understand potential systematics, compare transmission spectra at overlapping and neighboring wavelength regions, confirm throughputs, and determine overall performances. In our search for transiting exoplanets that are well suited to achieving these goals, we identify 12 objects (dubbed "community targets") that meet our defined criteria. Currently, the most favorable target is WASP-62b because of its large predicted signal size, relatively bright host star, and location in JWST's continuous viewing zone. Since most of the community targets do not have well-characterized atmospheres, we recommend initiating preparatory observing programs to determine the presence of obscuring clouds/hazes within their atmospheres. Measurable spectroscopic features are needed to establish the optimal resolution and wavelength regions for exoplanet characterization. Other initiatives from our proposed ERS program include testing the instrument brightness limits and performing phase-curve observations.

Kepler's Emergency Seems to Have no Long Term Effects

NASA’s Kepler spacecraft has suffered no long-term effects from an anomaly last month that threatened the mission, and the spacecraft should be able to operate for at least two more years, the mission’s manager said May 10.

At a press conference to announce new exoplanet discoveries in data collected by the spacecraft, mission manager Charlie Sobeck said the spacecraft had fully recovered from an “emergency mode” in April that disrupted science observations for more than two weeks.

“It looks at though it was a transient event,” he said of the incident that triggered the emergency mode April 7. “We don’t see that the spacecraft is operating any differently today than it operated before the emergency mode.”

link.

The Golden Eye of the JWST

link.

Kepler Resumes Science Operations

Two weeks after going into an emergency mode that jeopardized the mission, NASA’s Kepler spacecraft has recovered and resumed normal science operations, the agency announced April 22.

In a statement, Charlie Sobeck, the Kepler mission manager, said that the spacecraft had resumed science operations as of 11:30 a.m. Eastern April 22. The spacecraft is now beginning the latest observing campaign for its extended mission, known as K2.

Kepler was scheduled to begin those observations earlier in the month, but when spacecraft controllers made contact with the spacecraft April 7 they found the spacecraft was an emergency mode, which NASA describes as the lowest operational mode of the spacecraft. The mission declared a spacecraft emergency to gain priority access to the Deep Space Network to recover the spacecraft.

Controllers were able to restore control of Kepler by April 10 and exit emergency mode, gradually bringing back up the spacecraft’s various system. That process found no evidence of damage to the spacecraft, allowing science observations to resume.

The cause of the problem that triggered the emergency is still under investigation, but Sobeck said that some kind of “transient event” may have triggered a series of false alarms that overwhelmed the spacecraft’s computers. “Power-cycling the onboard computers and subsystems appears to have cleared the problem,” he said. “We’ve returned to science data collection while the investigation proceeds.”

link.

Kepler out of 'Emergency Mode'

NASA's Kepler spacecraft, the most prolific exoplanet hunter of all time, has bounced back from a mysterious glitch and may be able to resume operations soon.

Mission managers succeeded in getting Kepler out of "emergency mode" (EM) Sunday (April 10), and the space telescope is in a stable state with its antenna pointed toward Earth, allowing communications to resume.

"Once data is on the ground, the team will thoroughly assess all onboard systems to ensure the spacecraft is healthy enough to return to science mode and begin the K2 mission's microlensing observing campaign, called Campaign 9," Kepler mission manager Charlie Sobeck, of NASA's Ames Research Center in Moffett Field, California, said in a statement. "This checkout is anticipated to continue through the week."

link.

Kepler Enters "Emergency Mode"

Spacecraft controllers are working to restore control of NASA’s Kepler astronomy spacecraft after it entered an “emergency mode,” disrupting science observations, the mission’s manager said April 8.

In a statement, Charlie Sobeck, Kepler mission manager, said that spacecraft operators found the spacecraft was in emergency mode during a scheduled communications session with the spacecraft April 7. Sobeck described that emergency mode as the spacecraft’s lowest operational mode and is “fuel intensive.”

Kepler appeared to enter emergency mode about 36 hours before the communications session, but Sobeck didn’t state what might have caused the incident. The spacecraft was operating normally during its prior communications session April 4.

link.