Rattlesnake Mountain Observatory

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1 The Alliance for the Advancement of Science Through Astronomy Engage... Encourage... Enlighten AASTA Home > (RMO) is a professional-class astronomical research facility located at the summit of Rattlesnake Mountain, about 27 km (17 miles) northwest of Richland, Washington. AASTA Home Contributors and Supporters Educational Initiative "Stars On-Line" Rattlesnake Mountain Observatory Image Gallery Geographic Details Longitude: W Latitude: N Height (above mean sea level): 1050 meters Local Standard Time = UTC - 8 hours The observatoryʼs primary astronomical instrument is a 0.8-meter Cassegrain-style reflecting telescope, housed in the large (24-foot diameter) dome in the lower portion of the photograph at left. The telescope was designed, constructed, and installed at the observatory in 1971 by scientists working at, what is now, Pacific Northwest National Laboratory (PNNL). Rattlesnake Mountain is the highest elevation within a 100-km (60-mile) radius. A significant portion, including the observatory, lies within the ecologically sensitve FitznerEberhardt Arid Lands Ecology (ALE) Reserve an area of shrub-steppe wilderness largely untouched by human activity. The photograph at right was taken from the lower portion of the access road which runs across the Reserve and up to the observatory. The semi-arid conditions of the Lower Columbia Basin provide some of the best climatic conditions for astronomical work in Washington State. The area enjoys over 200 clear days per year, low humidity, and less than 7 inches total annual precipitation. Although clear skies are quite common throughout the year, an especially clear period starts at the beginning of July and lasts well into October. 1 of 7 10/7/08 4:48 PM

2 One of the first uses of the telescope was to support the on-going studies of auroral phenomena in Earthʼs upper atmosphere high above the Pacific Northwest. Over the next several years, the instrument was key in other research projects many involving Saturnʼs moon Titan, white dwarf stars, and searches for black holes. Around the mid-1980s, much of the research activity had ceased, and for the next 10 or so years, the telescope, and the rest of the observatory, had been relegated to "mothballed" status. The mounting, the optics, the hardware for mechanically moving it to point at different objects in the sky, and the electronics for interacting with the hardware, were all custom-designed for this specific instrument. In essence, no other telescope precisely like it exists in the world. Moreover, this telescope was a pioneer in the use of friction rollers to effect its motion as opposed to gears. And it remains the largest, most powerful, optical research-grade telescope in Washington State. 2 of 7 10/7/08 4:48 PM

3 AASTA assumed management and operational authority of the observatory in 1996, with the goal of refurbishing and upgrading the telescope so that it may become a resource for enhancing opportunities science education. By this time, the telescope was showing significant deterioration. Rust spots were appearing on the outside of the tube, and the control electronics (below), while still functional, no longer provided reliable positional information of the telescope. 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 were mechanically sound (albeit with evidence that some creative repairs had been made over the years). At the time of the projectʼs inception, the World Wide Web was just beginning to see widespread use, and some promising software technologies, including Java applets, were coming into being. Remote access to the telescope was to be accomplished through the development of custom Java applets that would appear in the userʼs web browser. These applets would present a view of the telescope in way such that its operation was as intuitive as possible. User interactions would be communicated back over the Internet to the telescope control computer (TCC), which would activate the telescope hardware to carry out the userʼs command. Data, most likely in the form of images, would be transmitted back to the userʼs computer for processing and analysis. This approach has some distinct advantages. The applet code that provides the interface is resident on, and hosted by, a web server, which is under the control of observatory staff. No special software is needed on the userʼs computer other than one of the widely available (and free) web browsers, such as Microsoft Internet Explorer, Netscape Navigator, or Firefox. Modifications to the interface code, perhaps to correct undesired behavior, or to enhance the operation, could be applied at the observatoryʼs web server, without requiring software upgrades 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 possible to tailor the interface according to the level of sophistication of the user. A classroom of students in a middle-school would see a different interface to the telescope than a graduate student in astronomy. Additionally, there is no geographic restriction to using the telescope; users from 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

4 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 a failure should occur, it must be able to detect it, put itself into a safe state, and alert observatory personnel to the situation. The telescope would be used primarily for science education, so the interface presented to the user must be intuitive. More often than not and this is particularly 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 today might call Internet-ready. Hardware incompatible with its new role would need to be removed and excessed; the remainder would need to be refurbished to operational quality, involving a great deal of mechanical and electrical work. Moreover, no commercial market exists that directly supports telescopes of this size; the collection of hardware devices that effect its operation is unique to this instrument. Any control software 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 made tremendous progress. Since the project inception, these volunteers have... Refurbished the optical encoders on each of the two axes of the telescope to provide precise positional information Replaced the old stepper-motor drive system with a high-quality servocontrolled motor system Identified, purchased, and installed an industrial-grade rack-mount computer (plus expansion cards) for controlling the telescope and its subsystems Upgraded the power to the dome, to accommodate the increased electrical demand of the new control systems Designed and developed software for interacting with the various systems, and integrating their behavior into a comprehensive control and automation system, with object selection and quick access to positional and other information from on-line star catalogues 4 of 7 10/7/08 4:48 PM

5 Designed and built a digital hand-paddle to enable local operation of the telescope by an observer at the eyepiece Replaced the mechanically-operated dome control system with one that can be computer controlled Installed a fiber-optic computer network and 11 Mbps and 256 kbaud radio-modem computer links to the PNNL, 17 miles away 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 well as astronomical video cameras for obtaining images (both static and dynamic) of celestial objects Cleaned the mechanical and optical components of the telescope, and repaired the neoprene sealing on the dome The concurrent fundraising and public outreach activities have supported the purchase of equipment, provided for teacher and student stipends, and paid the annual insurance bill. We have received cash and equipment grants from corporations such as Microsoft, Battelle, Hewlett-Packard, Numatec, and Bechtel-Hanford. The servo-based drive-motor system, worth about $36,000, was donated by the U.S. Department of Energy. We have received cash donations from over 300 members of the local community. We have hosted scores of tours at the observatory (as seen at right), each involving a couple dozen individuals. We have made many presentations to school, church, and community groups. To date, some $200,000 in donations, equipment, volunteer labor, grants, and in-kind contributions has been raised for this project. The current monetary value of the facility is estimated to be about $500, of 7 10/7/08 4:48 PM

6 The 0.8-meter telescope is now under local computerized control. An observer, located within the dome, can control the telescope and dome through interaction with the graphical interface on the telescope control computer. From the computer, the user may select a celestial object such as a star, major planet, the moon, star clusters, or galaxy from one of the programʼs on-line celestial databases, and invoke the telescope to go to that object. For each object chosen, the program calculates the effects of precession, nutation, and aberration to the coordinates of the object as read from the catalogue. It then reads the system clock, and (using the geographical location of the observatory and factoring in the effect of atmospheric refraction), calculates the position of the object in the local sky. In the case of solar system objects, such as the moon or one of the major planets, the program will first calculate the position of the object within its orbit around the sun. Depending on the object, these calculations may involve hundreds of terms. When the position of the object is determined, the program reads the position of the telescope, and (accounting for the rotation of the earth while moving to the new object) determines how far the telescope needs to move on each of its two axes. Simultaneously, the program instructs the dome to move to the azimuth position of the object. All these calculations take place within the span of a few milliseconds, imperceptible to the user. The telescope is then moved on each of its two axes in such a way as to eliminate the possibility that it is ever pointed below the horizon at any time during the move. When the target object has been reached, the program enters a tracking mode, whereby a small velocity is applied to one of the two drive motors in order to follow the object as it moves across the sky, due to the effect of the earthʼs rotation. A positional feedback algorithm within the program reads the encoders every 250 milliseconds, calculates the actual velocity of the telescope, and adjusts the speeds on the motors accordingly so as to maintain a constant tracking motion. During tracking, the user may use the hand paddle to adjust the position of the telescope. The program reads the state of the hand paddle several times per second and applies a velocity to the motors if it detects that one of the four directional buttons is pressed. A shift mode on the hand paddle allows the observer to rotate the dome. The program also includes utilities for testing the various hardware components, for calibrating the position of the telescope using observations of identifiable stars, and for determining the ratio of motor velocities to actual axis velocities. Additional utilities are needed for tuning the feedback algorithm this will ensure smoother, more efficient tracking and for quantifying and refining the pointing accuracy of the telescope. 6 of 7 10/7/08 4:48 PM

7 Having the telescope under local computerized control is the necessary prerequisite for remote access. The logic for moving the telescope from one target to the next is now 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 receive and respond to commands which come from another computer. These commands would transmit the coordinates of the target to which to move the telescope, and theoretically could come from anywhere on the planet. In practice, measures will need 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 telescope hardware into a dangerous state. It is highly likely that the selection of celestial targets will need to be separated out of the main control program and into its own separate application on another computer. This second computer would then act as the client to the telescope control computer, the latter then would have as its sole responsibility the accurate positioning and tracking of the telescope, and the operation of the auxiliary components, 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 any given instant. The client application would provide access to the databases of celestial objects, and allow the user to choose the object of interest and transmit it to the control computer. In essence, this client application would be the functional model for the eventual Java applet by which a user would interact with the telescope from a remote location, such as a classroom, via a web browser. Published 31 January 2007 Direct Comments and Inquiries to AASTA Webmaster Copyright 2007 The Alliance for the Advancement of Science Through Astronomy 7 of 7 10/7/08 4:48 PM