MICRONERVA - my "moon shot"

I finally updated my research group web page, admittedly more than halfway though a busy semester!   On my web page you can meet the new students in my research group, along with new articles and podcast appearances, and a description of our new masters degree emphasis in astronomy.  Now it is time for a new blog post too!

This past summer MICRONERVA started to take up residence at Baker Observatory.  In this post I will highlight the work of Central Methodist University senior physics major Denise Weigand, and how we went from a drawing on a Powerpoint slide to the built frame for the MICRONERVA prototype enclosure.

Denise was funded as a Missouri SpaceGrant Consortium intern to come work with me at Missouri State University.  I spent most of my summer traveling on the east coast (two immediate family weddings, a couple conferences, etc.), so we had to work remotely.  For that, we used Google+ Hangouts to share screens, audio and video to communicate effectively from a distance.

First, a bit about MINERVA, the "parent" observatory concept behind MICRONERVA.  For a number of years I've been helping with the more complex, larger version called MINERVA.  It's designed to be completely robotic and autonomous after initial setup and regular maintenance:

The basic principle behind MINERVA is to synthesize a larger telescope aperture by combining the light from multiple, smaller telescopes at a lower cost.  The cost of a telescope has a steeper than linear dependence on the telescope primary mirror area:

The cost of single aperture telescopes (red and blue data points) compared to multiple aperture telescopes (green data points).  The solid lines in red and blue indicate approximate power law relationships.  The jump at a diameter of ~1.2 meters marks the transition from the amateur market to the lower demand market that is partially dictated by military expenditures.  From Figure 1 of Swift et al. 2015.

For seeing-limited telescopes there is no loss in angular resolution, which is true at visible wavelengths for any primary mirror larger than ~8-inches in diameter without adaptive optics.  Additionally, the spectrograph shrinks in volume as N^3/2, where N is the number of telescopes, making it a lot cheaper and more stable too. In the case of MINERVA, four 0.7 m telescopes need a spectrograph 1/8^th the volume of a spectrograph for a single 1.4 m telescope.  Thus, one saves costs on both the telescopes and the spectrograph.  And because the spectrograph is smaller, it makes it easier to measure precise radial velocities to hunt for exoplanets.  It's a win-win situation all around.  As far as I know, MINERVA is the first successful on-sky demonstration of this multi-telescope approach for precise spectroscopy.  One of the enabling technologies are fiber optics, which allow us to bring together the light from several telescopes to a single spectrograph entrance slit.

Anyway, back to MICRONERVA.

Upon my arrival at Missouri State University in the fall of 2014, I saw that we had a number of computer controlled CPC800 Celestron Telescopes lying around for educational use.  I also noted that with a simple tip-tilt adaptive optics, light could be effectively coupled from these eight-inch telescopes into special optical fibers called single mode fibers.  In other words, we could build a mini-version of MINERVA - aka MICRONERVA - if we could effectively turn these telescopes into computer controlled autonomous robots.  Additionally single mode fibers provide the ultimate limit in the stable illumination of spectrographs, critical for measuring precise radial velocities.

We decided to start with a prototype of array of four telescopes, but this concept is extremely scalable and even cheaper than MINERVA.  I envision a future array of many hundreds of these telescopes, similar to the HATPI concept by Gaspar Bakos for exoplanet transit searches, but this time for spectroscopy.  I find this is a potentially more cost effective approach for large aperture spectroscopy compared to other concepts such as the Mauna Kea Spectroscopic Explorer:

HATPI concept design

Fast forward to the spring of 2016.  My former student Claire Geneser, now a graduate student at Mississippi State University, managed to get the telescopes to point to a series of targets entirely under the control of a laptop computer:

We still had a number of issues to solve - could we guide at <1 arc-second precision?  Could we control all of these telescope autonomously from a web page?  I'll post about our progress on these challenges at a later date.  We also needed an enclosure to hold the telescopes, something that could open and close on its own.  That is the problem Denise chose to solve.

Denise joined my research group in mid-June of 2016. We had looked into buying a pre-built "dome" like the excellent domes from Astrohaven.  However, at costs of >$25,000, these were beyond the limits of our modest budget.  We were going to have to build one ourselves. Our prototype telescope array will be located at Baker Observatory, shown below:

Baker Observatory, north of Marshfield, MO, the birthplace of Edwin Hubble

In the photo above you can see two traditional telescope domes that are the usual landmark for an observatory.  However, these domes are far more complex than necessary to build an autonomous robotic facility.  Between the lower shutter, dome slit, and dome rotation, three separate motors are needed to open, close and point the dome.  A far simpler approach for autonomy is to design an enclosure that needs only one motor to open and close.  One motor is much easier to program and control than three, even if the end result isn't as exciting as looking at the domes above.

Below is the first sketch Denise and I made of what would eventually be our prototype enclosure in mid-June. This drawing was made with Powerpoint while we talked on Google+ hangouts more than 1000 miles apart:

The first MICRONERVA enclosure sketch.

The design involved the smallest number of exterior surfaces - five - and a single motor to make the design as simple as possible (one of the guiding principles in our design process).  It wasn't our first design, but it was the first design to make sense.  The four shapes inside the triangular room represent the envelops of the four telescopes - e.g., the space they will fill after going through all possible directions they point.  The red surfaces for the roof, the triangles the side walls, and the rectangles some legs to hold the structure off the ground, to prevent moisture wicking and contact with snow in the winter.   The whole thing would be oriented east-west, to enable the largest declination range viewable, at the expense of some east-west horizon obscuration by the triangular walls.

Denise set about her summer turning this sketch into reality.  First up was getting the dimensions right, and here were some sketches that passed back and forth between us.  We started with Powerpoint because it had an easier learning curve than AutoCAD, and let us quickly iterate on ideas.

 

At the end of June, it was time to graduate to three dimensions, which we used Google Sketchup to get started:

We also started thinking about how the roof would roll of and on.  We had already settled on this excellent motor drive from MVO Controls:

Denise made a parts list, and readied to go to Lowe's and Home depot to acquire the wood we needed.  We decided to start with wood rather than aluminum or metal, since it was more forgiving of us to make mistakes, and it was cheaper too.  We'd learn our mistakes on this prototype, which would make things easier the second time around if we went for more permanent and expensive materials.

We next enlisted the help of our campus mechanical engineer, Brian Grindstaff, to help with some of the engineering logistics - e.g. building the floor like a deck with joists and slatted cross-beams and such.  For the first three weeks in the July heat, Denise and Brian build the decking floor and roof frame in the loading dock outside our departments building.  Having it on campus made it easier to work on every day, but then we'd have to transport it out to Baker Observatory, a 40 minute drive!

Brian helped Denise put her design into AutoCAD, and pick the roofing material, wheels, wheel channel. and many other practical aspects of our design under Denise's guidance.

By August 8th, Denise and I used Google maps to plot a final location for the enclosure at Baker Observatory, next to my colleague Dr Mike Reed's robotic 16-inch telescopes, BORAT.  It was ready to ship! The night prior Denise and I went to Baker Observatory with wooden stakes, string and a level, and staked out the position of the enclosure and made sure it'd be on ground that was level enough to be fixed with a shovel and some sweat.

To get the enclosure to Baker Observatory, we made the enclosure relatively easy to disassemble into three pieces - the roof, the deck floor, and the extension for the rails when the roof is "open".  We transported it on one of my students 16'x8' trailers.

The morning of August 9th, we loaded the enclosure onto the trailer.  We left as early as possible to beat the Southwest Missouri summer heat and humidity.  I also recruited my entire research team to help with the lifting and moving.  We had gotten good at this teamwork, because back in June we built a fence at the observatory.  We used reclaimed wood from a long fence in my subdivision that had been torn down and replaced after a pickup truck crashed through it:

Missouri State physics majors Joe Huber and Ryan Hall

Fence building at Baker Observatory in June of 2016 to help with car headlights during our public viewing nights.  Featuring Missouri State CS majors Frank Giddens and America Nishimoto, physics major Laura Ketzer, and Dr. Mike Reed.

Unloading the enclosure pieces on August 9th took a lot of work, and we were all very dehydrated by midday:

Lifting the roof onto the platform was the hardest part.

Denise Weigand next to her roll-off roof enclosure design built and installed!  August 9th, 2016

Two days later we came back and added cross-beam support to the legs, and the roof panels:

We'd add the walls by the end of that week in August.  Denise returned to Central Methodist University for her senior year. Today, the enclosure is buttoned up, complete with tornado tie-downs to keep it from getting blown over:

It's not quite ready for the MICRONERVA telescopes yet. We're waiting on funding to add some interior environment control. The motor has been tested and rolls the roof on and off.  I'll update on the other aspects of MICRONERVA in a future blog post.