《宽视场红外巡天望远镜WFIRST系外行星数据挑战#1》

  • 来源专题:天文仪器与技术信息
  • 编译者: zwg@niaot.ac.cn
  • 发布时间:2016-10-20
  • WFIRST当前处于Phase A 阶段,要定义其科学和仪器性能要求。

    Welcome to the WFIRST Exoplanets Data Challenge #1! The WFIRST mission is currently in Phase A, during which time the science and instrument performance requirements will be defined for exoplanet imaging and spectroscopy. In order to provide the project with the best possible inputs before the end of Phase A in 2017, we are seeking participation from teams with spectral retrieval expertise through the WFIRST exoplanets data challenge.

    The Challenge will run from August 15 to November 15, 2016. The 2016 Challenge consists of a blind spectral retrieval exercise using simulated, extracted spectra for several known RV and/or hypothetical discovery exoplanets. The spectra will NOT need to be extracted from simulated IFS data. Instead, we will explore the impact of signal-to-noise ratio and spectral resolution on the detection/measurement of atmospheric abundances and other planet properties. Even with that relatively simple goal, we expect the Challenge to be non-trivial!

    Incentive to Participate: While defining the first space-borne exoplanet imaging mission is hopefully its own compelling reason for doing this, to make this a little more fun the WFIRST Data Challenge Science Investigation Team is offering travel expenses and registration costs for one person on each team that fully completes the Challenge (all four planets, all SNR and R values, all requested retrieval outputs) to attend the 2017 WFIRST Science Meeting, or another exoplanets meeting of his/her choice (up to $2000).

    Participation in the Challenge is contingent upon acceptance of terms which will be included in the invitation email.

    If you wish to participate, please register and you will be sent an invitation.

    If you have questions, please forward them to Margaret Turnbull and David Ciardi through the "Contact" link above.

    We look forward to working with you this Fall!

  • 原文来源:https://wfirst.ipac.caltech.edu/sims/CGI_Data_Challenges.html
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  • 《美国空间大视场红外巡天望远镜(WFIRST)星冕仪通过第七轮里程碑评估》

    • 来源专题:天文仪器与技术信息
    • 编译者:zwg@niaot.ac.cn
    • 发布时间:2017-01-02
    • A Webex review of Milestone #7 for the WFIRST coronagraph technology programwas held on September 15, 2016. All five of the TAC members were able toparticipate in the review. Milestone #7 deals with the low noise detector requirements for the WFIRSTcoronagraph. When the noise requirements were specified several years ago, it wasnot clear if electron-multiplying CCDs (EMCCDs) would be suitable for use onWFIRST, or if the photon-counting readout technique would be applicable. As aresult of the error budget assigned to the detector at that time, the Milestone #7performance requirements for the detector and the readout electronics were set tobe a dark current less than 0.001 electrons/pixel/sec and a read noise less than 1electron/pixel/frame. Due largely to the decision to employ both EMCCDs andphoton counting threshold limits, both of these Milestone requirements have beenhandily met, even after exposure to radiation doses (multi-MEV protons) equivalentto over twice those expected during a six-year mission to and at L2. The measureddark current was 0.0007 electrons/pixel/sec, just below the requirement, and themeasured read noise was 1.7e-6 electrons/pixel/frame, nearly six orders ofmagnitude lower than required. In addition, the team demonstrated an ability tofurther adjust gains to deal with any unanticipated degradations, such as aging.While actual testing was conducted using COTS readout electronics, the TAC felt theteam’s design summarized for readout electronics based on space-heritagecomponents was sufficient at this time to support the milestone requirement fortesting with space-like electronics. Clearly both requirements of Milestone #7 havebeen met and exceeded. The tests also examined and reported on a number of othermeasures of the noise associated with the EMCCD/photon counting approach, inboth serial and parallel read-out mode, giving further support to the assertion thatthis approach should succeed. Meeting this Milestone on schedule implies that the project is still on its way tofinishing the WFIRST coronagraph Key Milestones on schedule. The TAC looksforward to learning about the progress made on the remaining two Key Milestones(#8 and #9), dealing with the OMC and PIAACMC coronagraph tests in the JPL HCIT,in both static and dynamic environments, the latter simulating the expectedperformance on a space telescope with pointing jitter. We thank Ben Parvin, Rick Demers, Leon Harding, and other WFIRST/AFTA-C teammembers for their presentations and comments during the review.
  • 《欧洲南方天文台8.2米望远镜系外行星成像器SPHERE见证系外行星诞生》

    • 来源专题:天文仪器与技术信息
    • 编译者:zwg@niaot.ac.cn
    • 发布时间:2018-07-06
    • SPHERE, a planet-hunting instrument on ESO’s Very Large Telescope, has captured the first confirmed image of a planet caught in the act of forming in the dusty disc surrounding a young star. The young planet is carving a path through the primordial disc of gas and dust around the very young star PDS 70. The data suggest that the planet’s atmosphere is cloudy. Astronomers led by a group at the Max Planck Institute for Astronomy in Heidelberg, Germany have captured a spectacular snapshot of planetary formation around the young dwarf star PDS 70. By using the SPHERE instrument on ESO’s Very Large Telescope (VLT) — one of the most powerful planet-hunting instruments in existence — the international team has made the first robust detection of a young planet, named PDS 70b, cleaving a path through the planet-forming material surrounding the young star [1]. The SPHERE instrument also enabled the team to measure the brightness of the planet at different wavelengths, which allowed properties of its atmosphere to be deduced. The planet stands out very clearly in the new observations, visible as a bright point to the right of the blackened centre of the image. It is located roughly three billion kilometres from the central star, roughly equivalent to the distance between Uranus and the Sun. The analysis shows that PDS 70b is a giant gas planet with a mass a few times that of Jupiter. The planet's surface has a temperature of around 1000°C, making it much hotter than any planet in our own Solar System. The dark region at the centre of the image is due to a coronagraph, a mask which blocks the blinding light of the central star and allows astronomers to detect its much fainter disc and planetary companion. Without this mask, the faint light from the planet would be utterly overwhelmed by the intense brightness of PDS 70. “These discs around young stars are the birthplaces of planets, but so far only a handful of observations have detected hints of baby planets in them,” explains Miriam Keppler, who lead the team behind the discovery of PDS 70’s still-forming planet. “The problem is that until now, most of these planet candidates could just have been features in the disc.” The discovery of PDS 70’s young companion is an exciting scientific result that has already merited further investigation. A second team, involving many of the same astronomers as the discovery team, including Keppler, has in the past months followed up the initial observations to investigate PDS 70’s fledgling planetary companion in more detail. They not only made the spectacularly clear image of the planet shown here, but were even able to obtain a spectrum of the planet. Analysis of this spectrum indicated that its atmosphere is cloudy. PDS 70’s planetary companion has sculpted a transition disc — a protoplanetary disc with a giant “hole” in the centre. These inner gaps have been known about for decades and it has been speculated that they were produced by disc-planet interaction. Now we can see the planet for the first time. “Keppler’s results give us a new window onto the complex and poorly-understood early stages of planetary evolution,” comments André Müller, leader of the second team to investigate the young planet. “We needed to observe a planet in a young star’s disc to really understand the processes behind planet formation.” By determining the planet’s atmospheric and physical properties, the astronomers are able to test theoretical models of planet formation. This glimpse of the dust-shrouded birth of a planet was only possible thanks to the impressive technological capabilities of ESO’s SPHERE instrument, which studies exoplanets and discs around nearby stars using a technique known as high-contrast imaging — a challenging feat. Even when blocking the light from a star with a coronagraph, SPHERE still has to use cleverly devised observing strategies and data processing techniques to filter out the signal of the faint planetary companions around bright young stars [2] at multiple wavelengths and epochs. Thomas Henning, director at the Max Planck Institute for Astronomy and leader of the teams, summarises the scientific adventure: “After more than a decade of enormous efforts to build this high-tech machine, now SPHERE enables us to reap the harvest with the discovery of baby planets!” Notes [1] The disc and planet images and the planet’s spectrum have been captured in the course of the two survey programmes called SHINE (SpHere INfrared survey for Exoplanets) and DISK (sphere survey for circumstellar DISK). SHINE aims to image 600 young nearby stars in the near-infrared using SPHERE’s high contrast and high angular resolution to discover and characterise new exoplanets and planetary systems. DISK explores known, young planetary systems and their circumstellar discs to study the initial conditions of planetary formation and the evolution of planetary architectures. [2] In order to tease out the weak signal of the planet next to the bright star, astronomers use a sophisticated method that benefits from the Earth's rotation. In this observing mode, SPHERE continuously takes images of the star over a period of several hours, while keeping the instrument as stable as possible. As a consequence, the planet appears to slowly rotate, changing its location on the image with respect to the stellar halo. Using elaborate numerical algorithms, the individual images are then combined in such a way that all parts of the image that appear not to move during the observation, such as the signal from the star itself, are filtered. This leaves only those that do apparently move — making the planet visible.