Rattlesnake Mountain Observatory

The Alliance for the Advancement of Science Through AstronomyEngage . . . Encourage . . . Enlighten

Rattlesnake Mountain ObservatoryAASTA Home > Rattlesnake Mountain Observatory

AASTA HomeContributors and

SupportersEducational Initiative

"Stars On-Line"Rattlesnake Mountain

ObservatoryImage Gallery

Rattlesnake Mountain Observatory(RMO) is a professional-classastronomical research facility located atthe summit of Rattlesnake Mountain,about 27 km (17 miles) northwest ofRichland, Washington.

Geographic DetailsLongitude: 119.59 W Latitude: 46.39 N

Height (above mean sea level): 1050 metersLocal Standard Time = UTC - 8 hours

The observatoryʼs primary astronomical instrument is a0.8-meter Cassegrain-style reflecting telescope, housedin the large (24-foot diameter) dome in the lower portionof the photograph at left. The telescope was designed,constructed, and installed at the observatory in 1971 byscientists working at, what is now, Pacific NorthwestNational Laboratory (PNNL).

Rattlesnake Mountain is the highest elevation within a100-km (60-mile) radius. A significant portion, including theobservatory, lies within the ecologically sensitve Fitzner-Eberhardt Arid Lands Ecology (ALE) Reserve—an area ofshrub-steppe wilderness largely untouched by humanactivity. The photograph at right was taken from the lowerportion of the access road which runs across the Reserveand up to the observatory.

The semi-arid conditions of the Lower Columbia Basinprovide some of the best climatic conditions for astronomicalwork in Washington State. The area enjoys over 200 cleardays per year, low humidity, and less than 7 inches totalannual precipitation. Although clear skies are quite commonthroughout the year, an especially clear period starts at thebeginning of July and lasts well into October.

Rattlesnake Mountain Observatory http://www.aastaonline.org/observatory.html

1 of 7 10/7/08 4:48 PM

The mounting, the optics, the hardware for mechanically moving it topoint at different objects in the sky, and the electronics for interactingwith the hardware, were all custom-designed for this specificinstrument. In essence, no other telescope precisely like it exists inthe world. Moreover, this telescope was a pioneer in the use of frictionrollers to effect its motion as opposed to gears. And it remains thelargest, most powerful, optical research-grade telescope inWashington State.

One of the first uses of the telescope was to support the on-goingstudies of auroral phenomena in Earthʼs upper atmosphere highabove the Pacific Northwest. Over the next several years, theinstrument was key in other research projects—many involvingSaturnʼs moon Titan, white dwarf stars, and searches for blackholes. Around the mid-1980s, much of the research activity hadceased, and for the next 10 or so years, the telescope, and therest of the observatory, had been relegated to "mothballed" status.


2 of 7 10/7/08 4:48 PM

AASTA assumed management and operational authority of the observatory in1996, with the goal of refurbishing and upgrading the telescope so that it maybecome a resource for enhancing opportunities science education. By thistime, the telescope was showing significant deterioration. Rust spots wereappearing on the outside of the tube, and the control electronics (below),while still functional, no longer provided reliable positional information of thetelescope.

The primary mirror (in the photograph below), at the base of the optical tube,had accumulated a layer of dust; its reflective coating was severely oxidized,and it had lost perhaps 50% of its original reflectivity.

Still, the telescope was operational, and the roller mechanisims weremechanically sound (albeit with evidence that some creative repairs had beenmade over the years).

At the time of the projectʼs inception, the World WideWeb was just beginning to see widespread use, andsome promising software technologies, including Javaapplets, were coming into being. Remote access to thetelescope was to be accomplished through thedevelopment of custom Java applets that would appearin the userʼs web browser. These applets would presenta view of the telescope in way such that its operationwas as intuitive as possible. User interactions would becommunicated back over the Internet to the telescopecontrol computer (TCC), which would activate thetelescope hardware to carry out the userʼs command. Data, most likely in the form of images, would betransmitted back to the userʼs computer for processingand analysis.

This approach has some distinct advantages. The applet code that provides the interface is resident on, and hosted by, a web server, whichis under the control of observatory staff. No special software is needed on the userʼs computer other than one of the widely available (andfree) web browsers, such as Microsoft Internet Explorer, Netscape Navigator, or Firefox. Modifications to the interface code, perhaps tocorrect undesired behavior, or to enhance the operation, could be applied at the observatoryʼs web server, without requiring softwareupgrades on the part of the end-user. The user would see the enhancements the very next time the telescope was accessed.

Java applets, if developed properly, are “write once, run anywhere”, meaning that the same applet will run on any of the popular platforms,including Windows, Macintosh, and Linux. Separate versions of the applet for each platform are not needed. Moreover, it is entirely possibleto tailor the interface according to the level of sophistication of the user. A classroom of students in a middle-school would see a differentinterface to the telescope than a graduate student in astronomy. Additionally, there is no geographic restriction to using the telescope; usersfrom the other side of the globe would access it just as easily as those within the local community.

Of course, this means a significant amount of work on the part of those operating the observatory. If the telescope is to function as a remote


3 of 7 10/7/08 4:48 PM

and automatic instrument, its operation must be smooth, reliable, and essentially fool-proof. It must be able to operate autonomously,scheduling observations according to the placement of objects in the sky, and deciding when weather conditions permit its safe operation. If afailure should occur, it must be able to detect it, put itself into a safe state, and alert observatory personnel to the situation. The telescopewould be used primarily for science education, so the interface presented to the user must be intuitive. More often than not—and this isparticularly true within the software development realm—if it is easy to use, it has been hard to make.

A telescope designed and built with late-1960s and early-1970s technology, no matter how “state-of-the-art” at the time, is not what we todaymight call “Internet-ready”. Hardware incompatible with its new role would need to be removed and excessed; the remainder would need tobe refurbished to operational quality, involving a great deal of mechanical and electrical work. Moreover, no commercial market exists thatdirectly supports telescopes of this size; the collection of hardware devices that effect its operation is unique to this instrument. Any controlsoftware that was to operate the telescope hardware and the auxiliary systems, would have to be developed “in-house”.

Despite the challenges, the team of dedicated and very talented individuals, working entirely as volunteers on behalf of AASTA, has madetremendous progress. Since the project inception, these volunteers have...

Replaced the old stepper-motor drive system with a high-quality servo-controlled motor system

Identified, purchased, and installed an industrial-grade rack-mountcomputer (plus expansion cards) for controlling the telescope andits subsystems

Refurbished the optical encoders oneach of the two axes of the telescopeto provide precise positionalinformation

Upgraded the power to the dome, toaccommodate the increased electricaldemand of the new control systems

Designed and developed software for interacting with the various systems, and integrating their behavior into a comprehensivecontrol and automation system, with object selection and quick access to positional and other information from on-line starcatalogues


4 of 7 10/7/08 4:48 PM

Designed and built a digitalhand-paddle to enable localoperation of the telescopeby an observer at theeyepiece

Replaced the mechanically-operated dome control system with one that can be computer controlled

Redesigned the secondary mirror focus motor control

Identified and purchased various optical elements (eyepieces,focuser, etc.) for local use at the telescope;Also identified and purchased a digital (CCD) camera, as wellas astronomical video cameras for obtaining images (bothstatic and dynamic) of celestial objects

Installed a fiber-optic computer network and 11Mbps and 256 kBaud radio-modem computerlinks to the PNNL, 17 miles away

Cleaned the mechanical and optical components of thetelescope, and repaired the neoprene sealing on the dome

The concurrent fundraising and public outreach activities havesupported the purchase of equipment, provided for teacher andstudent stipends, and paid the annual insurance bill. We havereceived cash and equipment grants from corporations such asMicrosoft, Battelle, Hewlett-Packard, Numatec, and Bechtel-Hanford. The servo-based drive-motor system, worth about $36,000, wasdonated by the U.S. Department of Energy. We have received cashdonations from over 300 members of the local community. We havehosted scores of tours at the observatory (as seen at right), eachinvolving a couple dozen individuals. We have made manypresentations to school, church, and community groups. To date,some $200,000 in donations, equipment, volunteer labor, grants, andin-kind contributions has been raised for this project.

The current monetary value of the facility is estimated to be about $500,000.


5 of 7 10/7/08 4:48 PM

The 0.8-meter telescope is now under local computerized control. An observer, located within the dome, can control the telescope and domethrough interaction with the graphical interface on the telescope control computer. From the computer, the user may select a celestialobject—such as a star, major planet, the moon, star clusters, or galaxy—from one of the programʼs on-line celestial databases, and invokethe telescope to go to that object.

For each object chosen, the program calculates the effects ofprecession, nutation, and aberration to the coordinates of theobject as read from the catalogue. It then reads the systemclock, and (using the geographical location of theobservatory and factoring in the effect of atmosphericrefraction), calculates the position of the object in the localsky. In the case of solar system objects, such as the moonor one of the major planets, the program will first calculatethe position of the object within its orbit around the sun. Depending on the object, these calculations may involvehundreds of terms.

When the position of the object is determined, the programreads the position of the telescope, and (accounting for therotation of the earth while moving to the new object)determines how far the telescope needs to move on each ofits two axes. Simultaneously, the program instructs thedome to move to the azimuth position of the object. All thesecalculations take place within the span of a few milliseconds,imperceptible to the user.

The telescope is then moved on each of its two axes—insuch a way as to eliminate the possibility that it is everpointed below the horizon at any time during the move. When the target object has been reached, the programenters a tracking mode, whereby a small velocity is appliedto one of the two drive motors in order to follow the object asit moves across the sky, due to the effect of the earthʼsrotation. A positional feedback algorithm within the programreads the encoders every 250 milliseconds, calculates theactual velocity of the telescope, and adjusts the speeds onthe motors accordingly so as to maintain a constant trackingmotion.

During tracking, the user may use the hand paddle toadjust the position of the telescope. The programreads the state of the hand paddle several times persecond and applies a velocity to the motors if it detectsthat one of the four directional buttons is pressed. A“shift” mode on the hand paddle allows the observer torotate the dome.

The program also includes utilities for testing thevarious hardware components, for calibrating theposition of the telescope using observations ofidentifiable stars, and for determining the ratio of motorvelocities to actual axis velocities. Additional utilitiesare needed for tuning the feedback algorithm—this willensure smoother, more efficient tracking—and forquantifying and refining the pointing accuracy of thetelescope.


6 of 7 10/7/08 4:48 PM

Having the telescope under local computerized control is the necessary prerequisitefor remote access. The logic for moving the telescope from one target to the next isnow in place, and the motion of the dome is synchronized with that of the telescope. The next step in this area is to provide the control program with the ability to receiveand respond to commands which come from another computer. These commandswould transmit the coordinates of the target to which to move the telescope, andtheoretically could come from anywhere on the planet. In practice, measures willneed to be taken that the commands received are originated from a trusted source,and that no command will be executed which threatens to place the telescopehardware into a dangerous state.

It is highly likely that the selection of celestial targets will need to be separated out ofthe main control program and into its own separate application on anothercomputer. This second computer would then act as the client to the telescopecontrol computer, the latter then would have as its sole responsibility the accuratepositioning and tracking of the telescope, and the operation of the auxiliarycomponents, such as the dome or the secondary mirror for focusing the telescope. It would retain the graphical interface that reports the state of the telescope at anygiven instant. The client application would provide access to the databases ofcelestial objects, and allow the user to choose the object of interest and transmit it tothe control computer. In essence, this client application would be the functionalmodel for the eventual Java applet by which a user would interact with the telescopefrom a remote location, such as a classroom, via a web browser.

Published 31 January 2007 Direct Comments and Inquiries to AASTA WebmasterCopyright 2007 The Alliance for the Advancement of Science Through Astronomy


7 of 7 10/7/08 4:48 PM

Documents

Rattlesnake Mountain Observatory