Background
The W. M. Keck Observatory operates two 10-meter optical telescopes featuring advanced instrumentation for optical and near-infrared wavelengths, including imagers, multi-object spectrographs, high-resolution spectrographs, and integral-field spectroscopy.
In 2022, the Keck Planet finder, the world’s most advanced high-resolution spectrometer for visible wavelengths, achieved its first light and began its exciting hunt for exoplanets. It’s an exciting step forward in advancing the search for habitable Earth-like planets.
As a nonprofit organization, Keck’s findings are used by the astronomy community worldwide. Astronomers apply to use the telescope, collect data, and after a proprietary period, this data is made public, contributing to global scientific knowledge.
Casebook Situation
The W. M. Keck Observatory, home to some of the world’s most powerful telescopes, aims to overcome unique technical challenges due to its location, setting a standard for astronomical observatories of its caliber. A few challenges the team tackles:
1. Atmospheric Disturbance: Although Mauna Kea is one of the best sites for astronomical observations, Keck still contends with atmospheric disturbances
that can affect image quality. Techniques like adaptive optics are used to correct these
disturbances in real time.
2. Instrumentation Maintenance and Upgrades: Keck’s telescope technology is highly sophisticated and requires regular maintenance and periodic upgrades to maintain cutting-edge performance. This includes updating detectors, spectrographs, and adaptive optics systems.
3. Light Pollution: While Mauna Kea is relatively isolated, light pollution remains a concern. Efforts to minimize light pollution are critical to maintaining the quality of observations.
4. Harsh Environmental Conditions: Mauna Kea’s high altitude exposes the observatory to extreme weather conditions, including low temperatures, ice, and snow, which can affect the instruments and the infrastructure.
5. Operational Complexity: Operating dual telescopes with multiple instruments requires sophisticated coordination and scheduling to optimize scientific output while accommodating maintenance, often done in harsh and rapidly changing conditions.
6. Remote Operations: While the observatory’s remote location offers advantages for clear-sky observations, it also complicates logistics, including the
transport of equipment and personnel.
Additionally, remote operations necessitate
robust telecommunications infrastructure.
7. Funding and Budget Constraints: Like many scientific
institutions, Keck faces ongoing challenges in
securing sufficient funding for operations, upgrades,
and research activities, often relying on public and
private funding sources.
About Keck Observatory
Astronomers worldwide use the W. M. Keck Observatory in Hawaii’s Maunakea to
observe the universe with unprecedented power and precision.
The twin Keck Observatory telescopes are the world’s most scientifically productive optical and infrared telescopes. Each telescope weighs 300 tons and operates with nanometer precision.
The telescopes’ primary mirrors are 10-meters in diameter, each composed of 36 hexagonal segments that work in concert as a single piece of reflective glass.
Resolution
Lilley and the team took comprehensive steps to ensure the Ronchi setup’s effectiveness for the KPF, including lab and field tests to validate the ADC’s performance and the optical design’s efficacy.
The Goals:
- Verify the performance of the Atmospheric Dispersion Corrector (ADC) through direct imaging.
- Use a crossed Ronchi grating to disperse the spot and optimize spot size and orientation over several elevations.
- Light is picked off after passing through the science triplet and is guided into a temporary direct imaging assembly.
Imaging Assembly:
- Utilizes a spare FIU Science triplet to collimate light, which ensures the proper input focal ratio.
- A Commercial Off-The-Shelf (COTS) lens and camera are used to image the spots formed where the Ronchi grating is located.
Optical Design and Setup:
- A 50mm COTS lens focuses light onto a camera (FLIR Blackfly S BFS-PGE-19S4M), which features a resolution sufficient to capture detailed spot dispersion.
- The setup includes optical components, such as a pellicle beamsplitter, ND filter, and various lenses, configured to optimize light input into the fiber and imaging system.
Lab Set Up
Testing and Results:
- Lab tests were conducted using a detailed setup that included fiber input, lenses, an iris stop, and a light source to simulate the conditions expected in astronomical observations.
- Zemax simulations were performed to evaluate dispersion with the ADC in a null position and with varying prism
rotations under a simulated 45-degree zenith angle.
- On-sky results and example images using the crossed Ronchi setup were presented, showing the system’s effectiveness in real observational scenarios.
Would you Recommend Applied Image products and services to others?
Mr. Lilley explained that they chose Applied Image for the Ronchi grating because they had the necessary specifications for the fiber injection unit (sizes and materials) readily available to customize to their needs.
The availability of these components and technical services was crucial as it allowed Keck to quickly implement the technology without the delays and costs associated with custom orders. Their confidence in their choice was supported by the successful use of these components by others in the astronomy community. The order process was straightforward, thanks to a user-friendly website.
More importantly, Applied Image’s technical sales team provided guidance from start to finish, recommending high-performance, cost-effective materials and providing timely and detailed quotes. The purchase was successfully completed through direct communication with the sales team, ensuring the accuracy of all specifications.
¹Pathak, P. et al. A High-precision Technique to Correct for Residual Atmospheric Dispersion in High-contrast Imaging Systems. Publ. Astron. Soc. Pac. 128, 124404 (2016).
Applied Image’s unique manufacturing processes and industry expertise allow us to create custom components and standards that meet the specific needs of our customers.