Photo credit: Alex Dzierba

About Us

Manoa Astronomical Technologies (MAT) is a Vertically Integrated Project (VIP) formed in 2015 with a focus on precision engineering for telescopes and astronomical instruments. The goal of VIPs is to engage undergraduates of all levels with graduate students and a faculty mentor to foster in-depth project-based learning. For the 2018-2019 academic year the MAT team is working in conjunction with the Institute for Astronomy (IfA) to develop a Filter Exchange Mechanism (FEM) for the UH88 telescope located on the summit of Mauna Kea on the island of Hawai`i.

Mission Statement

To cultivate an interdisciplinary Vertically Integrated Project (VIP) team that will gain hands-on experience in design and develop an understanding in optics and precision engineering through the design and fabrication of a filter-exchanging device for the IfA.

The team will:

  • Design a filter-exchanging assembly with cartridges that allows interchangeability between multiple filter options
  • Design a filter exchanging mechanism that can guarantee precision at various orientations (horizon-to-horizon and within UH88’s envelope)
  • Designed with the ability to house and protect filters without interrupting optical path
  • Designed with remote control capabilities

Project Overview

The outcome expected from this project is to have a functional filter exchanging device that will be mounted onto the UH88 Telescope by May 2019. The FEM is expected to be installed onto the back of the telescope within the next 1-2 years along with two new instruments which it will interface with.

For a complete list of requirements the filter wheel should meet, see: Functional Requirements under the Project tab.

Designing and constructing this filter exchanging device will not only benefit astronomers and astronomy students who study using the UH88 facility, but also allow future members to take this knowledge to enhance MAT’s own Pioneer 01-A and Pioneer 01-B telescopes. This project will teach important concepts on optics and space observation to engineering students who have no prior knowledge to this background. For this project, students from multiple disciplinary backgrounds will work together on designing sophisticated precision components that will benefit the Institute for Astronomy and its research efforts in the coming years. In addition to this, it will serve as a learning platform for both undergraduate and graduate students, as well as sets up a collaboration effort between the IfA and students and a potential local pipeline into observatories located in Hawaii.

Our Team

1st row (left to right): Daniel Vanta, Skye Nakamura, Sydney Inouye, Robert Scimeca, Jeanalyn Wadsack-Myers, Elise Sueoka
2nd row (left to right): Mervin Cash, Heather Situ, Jordan Florita, Bryant Higa

Advisors

A Zachary Trimble (Faculty Advisor, Dept. of Mech. Eng.)
Mark Chun (Faculty Advisor, IfA Hilo)
Melissa Onishi (Graduate Advisor)
Dayton Lee (Graduate Advisor)

Team Overview

UH88 telescope pointed at zenith

The UH 88 inch telescope (UH88) is a 2.2 meter Cassegrain telescope located at the summit of Mauna Kea. In 1970, it was the first telescope built on the summit, demonstrating the exceptional quality of the mountain for astronomical observation. Despite its relatively small size, UH88 has made many discoveries, the most notable include: the confirmation of the existence of the Kuiper belt, the discovery of 45 moons of Jupiter as well as moons of the outer planets, measuring the mass of the dwarf planet Haumea, measuring the size of the exoplanet WASP-10b and its contribution to refining the orbit of the asteroid Apophis, ruling out an Earth impact in 2027.

Back view of the UH88 telescope (with bottom Cassegrain instrument mounting flange)

As a Cassegrain telescope, incident light rays enter UH88 and come in contact with the primary mirror, it then reflects to the secondary mirror, and is redirected to a hole located at the center of the primary mirror, behind which the adaptive optics system, filter wheel and camera are situated. Filters are used in astronomy to limit the wavelength of light that reaches the camera’s charge coupled device (CCD) detector by absorbing all wavelengths except those specific to the filter’s bandpass. This specificity allows astronomers to more easily detect certain phenomena or gain insight on specific processes such as star forming regions. CCD detectors are monochromatic to ensure data fidelity, so in order to create a color image of the cosmos, multiple images of the same object are taken in different filters and stacked to produce the images of space we are accustomed to.

UH88 is currently undergoing a multi-year upgrade where it will be outfitted with a new camera that will increase its field of view by a factor of 4 and increase its resolution by a factor of 7. However, in its current configuration, the camera is incompatible with current instruments on the telescope due to size constraints in the optical path and the current filters being too small, limiting the field of view. For this reason, the Institute for Astronomy has commissioned MAT to build a new filter exchange mechanism that allows the UH88 telescope to fully utilize its camera and allow for compatibility with current and future optical instruments.

Project

When Galileo first observed the stars through his telescope, he could clearly see details of craters on the moon, but other celestial bodies looked like blurry faint objects to him. With advances in technology, modern telescopes can now see deep sky objects and study the origins of the universe. To enable further study in astronomy, the Manoa Astronomical Technologies team will cultivate an interdisciplinary Vertically Integrated Project (VIP) team, that will gain hands-on experience in design and develop an understanding in optics and precision engineering through the fabrication of a filter exchange mechanism for the IfA’s UH88 telescope.

The outcome expected from this project is to have a functional filter exchanging device that will be mounted onto the UH88 Telescope and it will fulfill the parameters that are stated in the functional requirements section below. Designing and constructing this filter exchanging device will not only benefit astronomers and astronomy students who study using the UH88 facility, but also allow future members to take this knowledge to enhance MAT’s own Pioneer 01-A and Pioneer 01-B telescopes. This project will teach important concepts on optics and space observation to engineering students who have no prior knowledge to this background. For this project, students from multiple disciplinary backgrounds will work together on designing sophisticated precision components that will benefit the Institute of Astronomy and its research efforts in the coming years.

Bottom view of UH88 telescope with instrument mounting flange and attached components (left) and allotted vertical spacing with expected UH88 setup (right).

This filter wheel should complete the following objectives.

  • Design a filter-exchanging assembly with cartridges that allows interchangeability between multiple filter option
  • Design a filter exchanging mechanism that can guarantee precision at various orientations (horizon-to-horizon and within UH88’s envelope)
  • Designed with the ability to house and protect filters without interrupting optical path
  • Designed with remote control capabilities

Below is the final CAD assembly of the filter wheel developed by the team.

Isometric view of assembled filter wheel with cartridges and gearing system

Subsystems

Optical Subsystem

The optics subsystem will be concerned with how each individual filter will be held and changed within the mechanism, paying special attention to the precision of the positioning of the filters within the cartridge as well as the cartridges’ position in the wheel. Additionally, the optics subsystem is responsible for fabricating filter cartridges that will house filters of varying shape and dimension.

Finalized filter wheel design

Cartridge designed to hold 100mm diameter filter

Cartridge designed to hold 165mm square filter

Cartridge designed to hold 152.4mm diameter filter

Structure Subsystem

The structure subsystem will be tasked with providing a housing for the entire system that is strong enough to handle the forces and moments imposed upon the filter mechanism, as well as take into account the pre-existing dimensional parameters supplied by the UH88. In addition to this, they are responsible for implementing a gearing system to allow the filter wheel to switch between the designated filter positions.

Filter wheel assembled with gearing system and placed in external housing, which will interface with Robo-AO and the Semiconductor Technology Associates (STA) camera

Electronics Subsystem

The Electronics subsystem will work to implement motorization and software that is compatible with the UH88 setup and will provide feedback on the position of each filter.

Selected microcontroller

Selected motor

Functional Requirements

Functional Requirements

Parameters

Justification/Notes

Filter housing must mount to Robo-AO and CCD Camera and shutter

Incoming light rays will be focused at approximately 10 in. from the bottom surface of UH88 to the detector of the STA camera

Filter housing shall maintain structural rigidity through various telescope orientations

The CCD camera weighs 90lbs and the mount must be able to withstand the moment created by this weight as the telescope moves. The IfA is also developing a new near-infrared camera (weight is 41 kg), which may also mount to the filter housing

Filter wheel shall house at least 4 filters, nominally 6, circular and square filters (the largest being 165 mm x 165 mm x 15 mm)

4 filters is the minimum amount of filters used in a single night and 6 filters is the total amount of filters available for use on the UH88

Filters shall be able to be swapped without system disassembly

Filters need to be easily accessible to allow swapping daily if need be in 30 min. or less (preferably less than 15 min.) by one to three person.

Shall account for CTE differences of materials

The housing must be able to withstand working temperatures of -5°C to 40 °C and storage temperatures of -15°C to 40°C. It is highly important that expansion/contraction of the filter housing do not damage the filter glass.

Protection of the filters while in enclosure

Filters must be protected to prevent dust, oil, or debris contamination

Filter pockets shall clear aperture on STA camera

The detector on the STA camera is 4” x 4”. To fully utilize its functions, the filter pockets is not to create any obstructions in the optical path including the focused cone of light and final image

Allow for remote operation

Filter wheel needs to be remotely controlled to take data and provide feedback of filter position as UH88 team cannot be at telescope 24/7

Shall implement initialization sequence (initiated when telescope is turned on and performs diagnostic checks)

Ensures proper functionality prior to filter wheel use

Shall implement re-initialization sequence

To confirm mechanisms absolute position, accounts for error, “reboot”

Shall switch filter positions in 30 seconds or less

To work with other subsystems

Constraints

Thickness of entire piece up to 2 in.

Space available after Robo-AO and STA camera installation

North-west dimension up to 24” N from optical axis and 13” S from optical axis and east-west dimension up to 28 in. (diameter).

Space available with electrical components on camera installed; should not interfere with other structures in UH88 as telescope moves about

No interfering light sources (e.g., no optical encoders)

Interference from light sources risks being read as false signal

No heat sources in optical path

Possible convection currents, might cause distortions as light travels through air with changing index of refraction

Filters shall maintain position repeatability of filters by +/- 9 μm in x- and y-direction with respect to mean position

During the positioning of changing filters the filter must align within a certain range to prevent image distortion and for calibration purposes.

Filters shall be centered on the optical axis to better than +/- 1 mm

Since the guide chip distance is 166.4 mm and the length of the filter is 165 mm, the guide chips will be vignetted. To ensure the largest field of view and minimum vignette, the filter must be accurately centered over the optical axis.

Schedule Overview

System Level Gantt Chart

Detailed overall scheduling for Fall 2018 through Spring 2019

Overview of project milestones for Fall 2018 through Spring 2019

Time Status

The upcoming milestone is to finalize the design for all subsystems in December and begin ordering prototyping materials for prototyping from December to January. The team is meeting objectives on time so current schedule is going according to plan. The team only needs more outreach opportunities to acquire additional funding to finish the project on time.

Finance Overview

The financial status of the MAT team is as follows, with the color-coded distribution per subsystem shown below:

Currently, MAT is funded for roughly $11,000, via funding accrued through the College of Engineering at UH Manoa. Fundraising efforts have been made as well, and will continue to be made in the upcoming Spring.

Want to get involved?

Team Meetings: Monday and Wednesday 5:00-6:00 pm at Holmes 300

Interested in Donating?

Contact our Financial Manager: sainouye@hawaii.edu, Sydney Inouye

Contact Information

Team email: astrotec@hawaii.edu
Project Manager: dvanta@hawaii.edu, Daniel Vanta
Financial Manager: sainouye@hawaii.edu, Sydney Inouye

Kinematic Couplings
Institute for Astronomy