Thread by @dr_guangtou

[1/n] Here is a thread about CSST (Chinese Space Station Telescope): A low-orbit, 2-m NUV-optical space telescope focusing on large sky surveys.

It is a separate module of the new space station and planned to launch around 2025.

[2/n] The telescope has an off-axis TMA design using SiC mirrors with some "active" capability for in-orbit adjustment.

It has ~1.1 deg^2 FoV for the main sky survey while having four separate small instruments. The designed resolution is around 0.12-0.15 arcsec.

[3/n] The main goal of CSST is a multi-band (NUV, u, g, r, i, z), large area (17500 deg^2) sky survey to r>25 mag that also has grism spectra coverage (r~22).

There is also a 400 deg^2 deep field and 1 or 2 much smaller UD fields.

[4/n] The main instrument is a very complicated camera for the main survey.

Instead of a sophisticated filter change mechanism, the focal plane may remind you of the original SDSS survey: each detector has a fixed filter on it.

[5/n] Another important component is a multi-channel imager (MCI) that can observe in three-band simultaneously.

It has a 7.7x7.7 arcmin FoV with 0.05 arcsec/pixel resolution. It will bring ~30 broad+medium+narrow band filters.

I call it "poor man's WFC3".

[6/n] CSST will also carry a small optical IFU instrument using an image slicer, mainly for scientific demonstration.

It has a 6x6 arcsec FoV, 0.2 arcsec spatial resolution, and covers 0.4-0.9 micron in wavelength with R>1000.

[7/n] Another interesting aspect of CSST is: it can dock to the space station for maintenance and upgrade in the future!

In the current design, >20 modules of the telescope can be replaced or have the potential for upgrade.

[8/n] Ok, now some honest Q&A

"Is CSST a new project that just pops up?"

No. It has been developed in the last 10 years, by people in different fields and all over China. The NAOC is leading most of the efforts on the science side. What you see is a huge amount of hard works.

[9/n] "Why I haven't heard about it?"

CSST involves a huge community. Chance is that if you ask Chinese astronomers about it, they will tell you something.

But it is true that the space agency hasn't really advertised it because of...culture difference?

[10/n] "Will it 'replace HST'?"

No. It is a very different telescope designed for a legacy survey that supports flexible science.

Also, in reality, the lack of certain resources and experience means many technical limitations.

After all, it is our first space telescope

[11/n] "Will the data be released?"

At this stage, there is no clear policy yet, but I bet with all my savings that there will be regular data release just like other surveys.

I will certainly advocate for that strongly and hopefully can help make it happen.

[12/n] "Will there be a 'Chinese STScI'?"

We are really just learning how to organize a project at this level from zero so...we will see.

Right now, NAOC will host the data center and there are four regional science centers to coordinate the scientific interests of everyone.

[13/n] Some personal notes:

I have been involved in CSST science preparation for a little bit, and it will be an important part of my plan for the next five years.

While being super excited about it, I also feel very nervous...

[14/n] Chinese astronomy community is still pretty new and relatively small. Compared to the American and European communities, we still lack the experience to handle such a complex space telescope project.

So there will a lot of trial and error...

[15/n] Luckily, we do have a group of brilliant young scientists working on it, and that gives me all the hope I need.

Hopefully, I can put this ambitious project on your radar.

And hopefully, we can develop many international collaborations using CSST data.