Written by Naoki Yasuda (Kavli IPMU) The galaxies PFS will observe are more than 8 billion light years away and their brightness is less than one to a 10 million of the stars visible to naked eyes. To measure the properties of these faint galaxies accurately, we have to develop data analysis software which can deal with various kinds of noises included in the acquired… Read more »
In July 2017, the Spectrograph Clean Room was finally built up on the fourth floor of the dome building at Subaru Telescope! Spectrograph Clean Room at Subaru Telescope It has been one year and a few month since the previous instrument was cleaned up from the floor, in order to accommodate four PFS spectrographs. Since then, floor has been reinforced,… Read more »
The PFS Science Team is now planning a large survey observation of the Universe using PFS. Three working groups have been discussing the plans to achieve their major scientific objectives: “Cosmology” research group to reveal the nature of dark matter, dark energy and neutrinos, “Galactic archeology” research group to reconstruct the history of the Milky Way Galaxy where we exist,… Read more »
For the PFS instrument, the lights from about 2400 astronomical objects are designed to be delivered through long fiber cable from the prime focus of the telescope to the spectrograph modules on the fourth floor in the dome building. This fiber cable subsystem, which is about 65m long in total, consists of 3 parts: (1) short cables accommodated into the… Read more »
For five days from July 3 to 7, the IAU (International Astronomical Union) Asia-Pacific regional meeting was held in Taipei, where the project manager Dr. Naoyuki Tamura (Kavli IPMU, project associate professor) gave a talk and introduced the current status of the PFS project, the instrument under development, and large-sky survey program under planning. Also, there was a poster presentation from… Read more »
At Laboratoire d’Astrophysique de Marseille (LAM), PFS Spectrograph Module (SM) is fully integrated and its performance is validated. As a part of these processes, two visible-red camera units are being tested; one is for thermal performance test and the other is for optical performance test. From 19th to 29th June, we got together at LAM and dedicated ourselves to joint… Read more »
PFS instrument catches light from about 2400 astronomical objects using fibers paved on the focal plane at the prime focus of the Subaru telescope, and each fiber is positioned by 2-staged actuator called “Cobra” (). As talked in the previous posts, 57 assemblies of Cobra positioners and fibers are integrated to one module, which is mounted to the optical bench…. Read more »
PFS is a spectrometer that disperses light and measures the intensity as a function of wavelength using photosensitive detectors. The operational bandpass for the PFS instrument covers the wavelengths from 380nm to 1260nm. The light delivered to the spectrograph is initially separated into three channels of blue, red, and near-infrared (NIR) by two dichroic mirrors. Each channel is deflected to… Read more »
In PFS observations, photons from the sky are fed into the optical fibers from one end on the Subaru prime focus, and are emitted out from the other end to feed the spectrograph. The prime focus and spectrograph are physically remote from each other, so the total length of the fibers that optically link them has to be approx. 60… Read more »
Among the PFS instrument subsystem, four spectrographs are developed under the leadership of LAM (Laboratoire d’Astrophysique de Marseille). Since 2015, the first spectrograph module has been integrated and tested for its performance. In this article, we’ll talk about integration and test activities at LAM. Below photo shows the Visible-Red camera unit under assembly: optical components were accommodated in the cryostat… Read more »
We will observe ~2400 objects using four identical spectrograph modules, each of which acquires ~600 spectra of astronomical sources and calibration sources. Each module covers wide wavelength range on visible and near-infrared band (380 — 1260 nm). To achieve this, the module has 3 camera units; visible-blue, visible-red and near-infrared. The light of each band is introduced by using two “dichiroic mirrors”, which split the light at a given wavelength.
PFSでは約2400個の天体を観測しますが、4つの同型の分光器を用いてそれぞれ600本のスペクトルを取得します。各分光器は可視光域から近赤外域までの広い波長範囲 (380 から1260 nm) をカバーする為、「可視光域青用」、「可視光域赤用」、「近赤外域用」の3つのカメラユニットを持っています。3つのカメラには、特定の波長で光を分けることのできるダイクロイックミラーを2つ用いて、光を導入します。
To measure the fibers position on the focal plane, “Metrology Camera System” is attached on the Cassegrain focus of Subaru telescope. Looking up to the prime focus (see this image from HSC blog for clear image), this camera takes a image of back-illuminated fibers. Thanks to a large format of ~50 M pixels CMOS sensor, this camera can acquire all ~2400 fiber spots in a single exposure. The camera system is also designed to execute the process from exposure to measurement of fiber centroids within 5 seconds. Effective measurement of the fibers position enables us to shorten overhead for fiber configuration and execute large statistical survey observation.
The Metrology Camera System will be delivered to Subaru in early 2018.
焦点面上のファイバーの位置を測定する為に、『メトロロジカメラシステム』をすばる望遠鏡のカセグレン焦点に取り付けます。このカメラは焦点面を見上げるようにして後ろ側から照らされたファイバーの画像を取得します(イメージ的にはこちらの画像 (HSCブログより) のような感じです)。メトロロジカメラには50Mピクセルの大判のCMOSセンサが搭載されているため、約2400本のファイバー像をたった一回の露出で得ることができます。また、画像の取得から各ファイバーの位置測定までを5秒以内に行うように設計されています。このようにファイバーの効率よく位置を測定することで、ファイバーの配置など観測準備にかかる時間をなるべく短くし、大規模サーベイ観測を行うことができるのです。
メトロロジカメラシステムは2018年4月にすばる望遠鏡へ搬送されるました。
The Spectrograph Clean Room is a room whose size is 6.7 m wide, 8.6 m long ,and 3.6 m high. Four PFS spectrographs will be accommodated in the clean room. To stabilize the spectrograph performance, the temperature in the room will be controlled at 5 +- 1 degree Celsius. Besides, a crane with capability of 500 kg is installed for assembly and maintenance of the Spectrograph.
分光器設置室は、すばる望遠鏡ドーム棟4階に建設された部屋で、幅6.7m × 奥行8.6m × 高さ 3.6 mの大きさです。 PFSの4台の分光器がこの部屋に設置されます。分光器の安定性を図るために、部屋全体が5±1℃の範囲で温度管理されます。また、分光器の設置やメンテナンス用に室内には耐荷重500kgのクレーンが設置されています。
