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Can Air Bearings Overcome the Issues at the Keck Observatory?

Can Air Bearings Overcome the Issues at the Keck Observatory?

Follow Our Air Bearing Enthusiast to Keck to Offer Design Improvements

Welcome to part two of our blog series where we continue following the story of one man whose interest in air bearings transformed operations at two world-class astronomy observatories. In part one, we met Peter Gillingham, an astronomy engineer who implemented New Way Air Bearings in a solution for the European Southern Observatory’s Very Large Telescope (ESO/VLT).

In part two of the series, we follow Gillingham to the Keck Observatory. Having previously served as Operations Director from 1992-1997, he is consulted for an independent design assessment for a new angular measurement device for the telescope.

No Longer Measuring Up

The first of the Keck Observatory telescopes began operations in the early 90s utilizing a mechanical roller track system with an encoder to determine the telescope pointing angle. Initially, the system worked well, but over time the disadvantages of a mechanical system came to bear.

Three Disadvantages of a Mechanical-Based Encoder

The drawbacks of the mechanical roller track system for the azimuth encoder included:

  1. Significant Maintenance
    The original azimuth encoder required periodic maintenance to apply oil for the encoder to roll on the track. While the oil was necessary for operations, it often would get on the tracks, causing potential contamination issues.
  2. Decreased Accuracy
    Despite the oiling, over time the natural wear from friction began affecting measurements. The friction from the mechanical roller track system coupled with the slow movement of the telescope (down to a nanometer) caused the encoder to ‘stick.’ As the encoder becomes ‘unstuck’ to move appropriately, vibration and jitter would occur, ultimately affecting the accuracy.
  3. Inefficient Operations
    Engineers spent significant time each night to find the target for observation. The accuracy of the encoder caused the observatory to be inefficient with the limited observatory time.

Despite trying to fix the existing solution, the obstacles remained. Given these limitations, Ean James, Staff Mechanical Engineer at the Keck Observatory, was tasked to upgrade the azimuth encoder to overcome the existing limitations. James and his team developed a proposed design utilizing a 12m rotary device to turn the encoder. The size of the ring presented implementation issues, so it was recommended he consult with Gillingham given his past experience at Keck.

Keck ObservatoryGillingham assisted with a new design, reducing the size of the encoder ring down to 1m, a more feasible design. The design required a bellows coupling which demanded extremely accurate angular coupling. To maintain this high angular accuracy, no considerable amount of torque could be applied. Gillingham knew the only way to achieve this was to remove friction.

“I was only too happy to suggest the encoder system needed an air bearing system at the bottom of the bellows coupling to maintain high angular accuracy,” states Gillingham.

By the time James consulted with Gillingham, New Way Air Bearings had been operating successfully for over 10 years at ESO/VLT. Gillingham introduced James to New Way Air Bearings as he knew their standard line of products were a good fit for this application.

New Way was the first company to offer a standard line of air bearings products featuring porous media. New Way’s Porous Media Technology utilizes naturally porous carbon to deliver a stiff cushion of air through millions of sub-micron sized holes. By removing friction in this manner, the air is evenly distributed, eliminating concerns of pressure gradients which can cause a failure of the air bearings as well as potential damage.

With this knowledge and proven operational experience, Gillingham was confident an air bearing solution would solve several problems for the azimuth encoder.

Three Benefits to Implementing Air Bearings in the Keck Azimuth Encoder

  1. Improved Precision
    The use of air uniformly distributed over the bearing face allows the encoder read heads to move not only with zero friction but also with zero stiction, providing nano-level precision positioning. For comparison, the team did investigate the use of a ball bearing but it would have introduced 100 times more friction than the system could handle; this would have twisted the bellows coupling, destroying the required accuracy.
  2. No Routine Maintenance
    With the use of air, the burdensome lubrication requirements of mechanical systems would no longer be a concern. Consequently, concerns over contamination from the oil would also be eliminated.
  3. Increased Operations Time
    With improved precision, less time would be spent trying to acquire the nightly observation target. Additionally, the lack of required maintenance would allow for more operations time. Together, this would result in more efficient use of the telescope, allowing for more observations.

Encountering Skepticism

Gillingham’s eagerness to suggest air bearings was met with lots of questions by James.

James had not worked with air bearings before, so was skeptical and had some hesitation.

  • What would happen if they got dirty?
  • Would the design affect their existing air supply, especially given their high altitude?
  • How would they be mounted to be able to tune/adjust?

A panel eventually decided to pursue the air bearing design as there were no other options they knew of to provide zero friction and its associated benefits. The team decided to push forward and prototype the solution.

Stay Tuned!

Join us for the final blog in the series where we learn what happened with the prototype at the Keck Observatory. Will James’ concerns come to fruition or will he become a believer in air bearings like Gillingham? Will an air bearing solution improve the operations at the Keck Observatory?

Until then, if you are ready to learn more about how air bearings can improve your application, contact us today for a complimentary consultation!