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M3 Engineering and Technology Corp. (M3) a full discipline architectural, engineering and construction management firm designed the site, infrastructure, enclosure and support facilities for the Space Surveillance Telescope Australia (SSTA) to site specific design requirements, Australian codes and standards, stringent Australia Department of Defense security stipulations and capable of sustaining cyclonic wind loads. This paper presents the design and construction challenges of the of this uniquely situated telescope observatory in the most active Australian cyclonic region. The SSTA is a joint project between the Australian Department of Defense and the United States Defense Advanced Research Projects Agency (DARPA). This project is part of the Space Surveillance Network, a worldwide network of 29 military radar and optical telescopes that observe and catalogue space objects to identify potential collisions. The telescope after going through an initial trial period at White Sands Missile Range, New Mexico is now at its permanent home in the furthest western point of Australia awaiting the completion of the observatory and support facilities. SSTA’s relocation to Harold E. Hold Naval Communication Station (HEH) near the Shire of Exmouth, Western Australia will allow the telescope to relay information quickly to the United States. It will be looking into the southern hemisphere from its strategic location, an area of the sky that according to DARPA is “sparsely observed.”1 Although the location is strategic for viewing and tracking purposes, it places the telescope in a cyclonic region, making the enclosure that protects the telescope very challenging to design and construct. Typically, astronomical observatories are designed to sustain survival wind speeds of 54 to 78-meters per second. However, given the extreme weather conditions in Exmouth, the SSTA observatory must survive 94-meters per second wind speeds and be operationally ready after the cyclonic event. The basis of design for the SSTA is the enclosure and support facility that M3 designed at White Sands Missile Range, New Mexico. The project site in New Mexico is a more traditional astronomical observatory site with normal survival wind loads and cooler temperatures. Temperatures in Exmouth typically vary from 12°C to 37°C and is rarely below 9°C or above 42°C. Exmouth also experiences extreme seasonal variation in the perceived humidity. Due to HEH’s site remoteness, two critical operational challenges in comparison to the base line New Mexico design influenced major changes to the SSTA observatory design. The unavailability of a mirror aluminizing facility within Australia and the risk of handling the primary and secondary mirrors with external cranes required the SSTA observatory to increase the enclosure diameter by 5.0 meters allowing the implementation of an overhead bridge crane and enough space to handle the mirrors internally within the observatory. The SSTA site is designed for a future aluminizing facility on site. These design requirements heavily influenced the architectural, structural and mechanism designs. The SSTA enclosure larger diameter and therefore heavier rotating enclosure along with the cyclonic wind loads and high angular dome rotational requirements required additional mechanisms compared to the New Mexico design. The azimuth bogie wheel diameter increased, and the quantity doubled to 16 total. The (8) azimuth drives units changed from 9.3kW to 56kW and the lateral and uplift restraint system implemented an additional 16 external lateral restraint arms to keep the enclosure from shifting during a cyclonic event. The relocation of the US based telescope and components designed to operate at 60Hz power frequency added complexity because the power at the SSTA site is 50Hz. M3 designed a stand-alone primary and backup power plant to Australian standard frequency of 50Hz. To minimize operational risks to the telescope, M3 implemented a frequency converter providing 60Hz power to the US designed telescope and components and 50Hz to the rest of the facilities. This allowed the observatory to comply with Australian codes and standards and the use of standard Australian 50Hz equipment for the facilities electrical and HVAC systems.
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