Software for two Xenics cameras!

Yep, you've read right: we now have two of the Xenics IR cameras. The first we purchased will be dedicated to the low-order wavefront sensor, the second will have the privilege of being our "science" detector for the commissioning of SCExAO, before we try and add HiCIAO, and might even be able to do some science itself!

Today, we finally managed to control both cameras from the same computer... hurray! This server/client architecture we've developed is actually proving very handy: one server per camera, each one awaiting for connections (via the local network or directly from the SCExAO control computer) listening to their special port number.

The client can now ask either of the cameras (or both) to take images, query for or update the camera configuration (exposure time, subarray mode, gain), or tell it to shutdown. Now that these detectors are both working, we can turn off the visible laser diode: this new year will be bright in the infrared for SCExAO!

SCExAO will be at SPIE (part 2)

Just like the title of the post says: part 2 of our massive submission of abstracts for the the next astronomy SPIE conference.

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Olivier submitted:

The Subaru Coronagraphic Extreme AO (SCExAO) system: Wavefront control and detection of exoplanets with coherent light modulation in the focal plane

The SCExAO system is designed to enable high contrast imaging at small angular separation (less than 0.5”) in the near-IR. It receives light from Subaru Telescope’s AO system and includes a second step of wavefront control and a high performance PIAA coronagraph. Light is then sent to the HiCIAO camera. For wavefront sensing, SCExAO uses a MEMS type deformable mirror to introduce known diversity in the pupil phase. The corresponding modulation is detected in the science focal plane, and leads to a measurement of the residual wavefront aberrations. The same modulation is also simultaneously used to differentiate residual scattered starlight (which is coherent with the light introduced in the focal plane by the modulation) from actual sources (planets, disks).

This combined wavefront control and coherent detection scheme is ideally suited for detection of faint companions at small angular separation. Detailed numerical simulations and recent laboratory results show that this techniques can calibrate and remove static and slow speckles which traditionally limit high contrast detections. A visible light lab prototype system at Subaru Telescope recently demonstrated speckle halo reduction to 2e-7 contrast within 2 lambda/D, and removal of static coherent speckles to 3e-9 contrast.

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Frantz submitted:

The Subaru Coronagraphic Extreme AO system: progress report

In 2009 our group started the integration of the SCExAO project, a highly flexible, open platform for high contrast imaging at the highest angular resolution, to be inserted between the coronagraphic imaging camera HiCIAO and the 188-actuator AO system of Subaru. In its first version, SCExAO combines a MEMS-based wavefront control system feeding a high performance PIAA-based coronagraph, that suppresses the central obscuration and the thick spider vanes while preserving throughput and angular resolution. It also includes a coronagraphic low-order wavefront sensor, a non-redundant aperture mask and a visible imaging mode, all of them designed to take full advantage of the angular resolution (40 mas in the H-band) that an 8-meter telescope has to offer.

Group pictures for December 2009!

Today, Vincent is leaving Hawaii to France for his "X-mas break"... because when he gets back in January next year, others will have left for good, we took a couple group pictures. The first one was taken in the office and from left to right you have: Frederic Vogt, Kaito Yokochi, Vincent Garrel, Frantz Martinache, Olivier Guyon and Takashi Yoshikawa. The second one was taken in the Subaru Simlab, right in front our our SCExAO clean booth. From left to right you have: Frantz Martinache, Frederic Vogt, Olivier Guyon, Vincent Garrel (standing), Kaito Yokochi and Takashi Yoshikawa.

Happy holidays Vincent and see you next year!!

Optical design schematic

Kaito Yokochi just made this nice schematic of the lab configuration of the SCExAO coronagraph. It'd be a pity not to post it here... thanks Kaito!

Cover panels snug fit

The protection cage introduced in a previous post was just a prelude... now we have some pretty good looking slick black panels to protect the bench from dust, light and coffee spills to complete the cover... take a look (picture courtesy of Takashi):

You may notice the transparent panels on the right side of the picture: it happens fairly regularly that visitors show up in the lab and want to see what the experiment looks like. We figured that a sneaky double panel system (transparent underneath the black) would let people see the guts of SCExAO and still protect the bench from things like unsuspected screwdriver attacks.

Before we complete the enclosure (on the sides), we need to neaten all the serial and USB cables that connect to the motors, actuators and cameras mounted on the bench.

The SCExAO project will be at SPIE (part 1)

Yesterday was the deadline for the submission of abstracts for the next SPIE Astronomical Instrumentation conference that will be held in San Diego, CA from June 27 to July 2, 2010. Pretty much everyone in the group decided to submit an abstract so I thought it'd be fun to gather them all here, as they draw a fairly coherent picture of the project... enjoy!

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Frédéric submitted:

The Subaru Coronagraphic Extreme Adaptive Optic (SCExAO) system : implementation and performances of the Coronographic Low Order Wave-Front Sensor

In order to achieve high-contrast imaging at small working angles using the HICiAO camera on the Subaru telescope, a Phase Induced Amplitude Apodization (PIAA) Coronograph system is currently being assembled. The Subaru Coronographic Extreme Adaptative Optic (SCExAO) system, scheduled to be installed on the telescope early spring 2010, is located between the Subaru Adaptive Optic system (AO-188) and the recently commissioned HICiAO camera. It is designed to achieve a 1e-6 contrast at separations less than 0.5". This high contrast coronographic imaging requires an accurate control of low order wave-front aberrations, such as tip-tilt and focus errors. Simulations and laboratory prototyping have shown that a Coronographic Low Order Wave-Front Sensor (CLOWFS), which uses a single defocused image of a reflective focal plane ring, can measure tip-tilt to an accuracy of 1e-3 lambda/D. We report the implementation and performances of the CLOWFS on the SCExAO system. Using both the CLOWFS camera as well as the science camera in the system, we quantify the accuracy of this system and its ability to successfully remove tip-tilt errors from the science image. We show that CLOWFS measurements can be used in post-processing to accurately remove coronographic leaks due to residual tip-tilt errors. We finally deduce the maximum contrast to be reached using the SCExAO system alongside the HICiAO camera and the AO-188 on the Subaru telescope.

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Kaito submitted:

An 8 Octant Phase Mask coronagraph for the Subaru Coronagraphic Extreme AO (SCExAO) system: system design and expected performance

The 8 Octant Phase Mask (EOPM) coronagraph is among the highest performance coronagraph concepts, and combines high throughput, small inner working angle, and large discovery space. However, its application to ground based telescope such as Subaru Telescope is challenging due to pupil geometry (thick spider vanes and large central obstruction) and residual tip-tilt errors. We show that the Subaru Coronographic Extreme Adaptative Optic (SCExAO) system, scheduled to be installed on the telescope early spring 2010, includes key technologies which can solve these problems. SCExAO uses a spider removal plate (SRP) which translates four parts of the pupil with tilted plane parallel plates. The pupil central obstruction can be removed by a pupil remapping system similar to the PIAA optics already in the SCExAO system, which could be redesigned with no amplitude apodization. The 8OPM is inserted in the focal plane to divide a stellar image into eight-octant regions, and introduces a pi-phase difference between adjacent octants. This causes a self-destructive interference inside the pupil area on a following reimaged pupil plane. By using a reflective mask instead of a conventional opaque Lyot stop, the stellar light diffracted outside the pupil can be used for a Coronographic Low Order Wave-Front Sensor (CLOWFS) to accurately measure and correct tip-tilt errors. A modified inverse-PIAA system, located after the reimaged pupil plane, is used to remove off-axis aberrations and deliver a wide field of view.
We show that this 8OPM coronagraph architecture enables high contrast imaging at small working angle on the Subaru telescope. Our approach could be generalized to other phase mask type coronagraphs and other ground based telescopes.

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Vincent submitted:

The Subaru Coronagraphic Extreme AO (SCExAO) system: Visible Imaging Mode

The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system is an instrument designed to be inserted between the Subaru AO188 system and the infrared HiCIAO camera in order to greatly improve the contrast in the very close (less than 0.5") neighbourhood of stars.
Next to the infrared coronagraphic path, a visible scientific path, based on a EMCCD camera, has been implemented. Benefiting from both AO correction and new data processing techniques, it is a powerful tool for high angular resolution imaging and opens numerous new science opportunities. A factor 2 to 3 in Strehl ratio is obtained compared to the AO long exposure time: up to 25% Strehl in the 650nm wavelength, depending on the image processing algorithm used and the seeing conditions. The system is able to deliver diffraction limited images at 650 nm (17 mas FWHM). Our baseline image processing algorithm is based on the selection of the best signal for each spatial frequency. We demonstrate that this approach offers significantly better results than the classical select, shift and add approach (lucky imaging). We report on the first on-sky visible imaging results.
We also describe how the SCExAO visible channel will also later host a high performance optical wavefront sensor based on a nonlinear curvature scheme.

Software for the Xenics IR camera

A couple of weeks ago, I blogged about the Xenics camera, which we finally were able to take images with. Since then, I have kept playing with the SDK to build an application that is better suited to our needs for SCExAO.

While it may not be the best file format in the world, all the astronomical instruments I have encountered so far produce FITS files as their final data product. The first thing to do was therefore to change the program the camera came with to make saving the data in the FITS format possible, which is fairly easy thanks to the cfitsio library.

Incidentally, that also improves the image quality. Indeed, the original program would produce what looked like 24-bit color bitmaps... but were in fact 8-bit greyscale only. That is very unfortunate since the camera uses 14-bit ADC... 6 bits of dynamic were simply lost in an elegant bitwise data shift. The image (also bias-substracted) looks somewhat better now that we make use of the entire dynamic range!

That also helped to neaten the code that originally had to be compiled with the wxWidget library, just because of the need to save bitmaps and read configuration files. While there is nothing wrong with wxWidget which is an attempt at providing a cross-platform widget library, it is just a little overkill to link it just to save bitmaps.

So what's next? We're still trying to figure out what is the best way to interface the camera with our already complex programming environment. At this point, I think it would be best to make it as standalone as possible, and one approach is to create a server program that would keep the camera up and running, and have other client programs connect to it via sockets to tell it to take pictures when needed. I just want to make sure that this socket communication system will not slow down the data acquisition... for one should not forget that one important use of this camera will be in the low-order wavefront sensor, which will be running at over 100 Hz for extended periods of time.

HiCIAO in the UK news

While SCExAO is still being integrated, HiCIAO is already operational and delivering some cool science data. The Daily Mail online shows a picture of the planetary candidates orbiting the G-star (i.e. Sun-like star) GJ 758 that was imaged during a HiCIAO engineering run in August 2009 at the Subaru Telescope.

SCExAO will allow to probe the innermost part of such planetary systems... and maybe uncover new planets in the habitable zone of nearby stars like GJ 758.