Communications challenge for the Gemini 8-m Telescop es James R. Wright Gemini 8-m Telescop es Pro ject 950 North Cherry Avenue Tucson, Arizona 85726-6732 USA ABSTRACT We discuss the requirements and design of the communications system for the Gemini 8-meter Telescop es Pro ject . This system is unique not only in our integrated approach to data, voice and video, but it also must span the glob e to reach the two telescop e sites in Chile and Hawaii, and provide access to astronomers around the world. We discuss the various services planned for the communications system, the many lo cations whichmust b e served, and the anticipated quality-of-service demands. The constraints which limit our options are also discussed. Finally we present our plans for meeting these challenges. Keywords: communications, LAN, WAN, video conferencing, telephony, ethernet, ATM 1. INTRODUCTION The Gemini Pro ject is an international partnership to build two 8-meter telescop es, one on Mauna Kea, Hawaii, and one on Cerro Pachon, Chile. The telescop es and auxiliary instrumentation will b e international facilities op en to the scienti c communities of the memb er countries. The pro ject includes not only the summit lo cations for the actual telescop es, but also base facilities in Hilo, Hawaii and La Serena, Chile; mid-level facilities at Hale Pohaku, Hawaii and Cerro Tololo, Chile; an International Pro ject Oce at a lo cation to b e determined; National Pro ject Oces in each memb er country; and all the home institutions for the user community. The communications system will b e critical to the success of the Gemini Pro ject. The following excerpt from the 1 \Communication Vision for the Gemini 8-m Telescop es" gives an idea of the extent to whichwe will dep end up on communications. It is nightfall on Cerro Pachon and the system op erator and sta astronomer are working through the b eginning of the night's queued observations. While the system op erator is watching the current satellite weather map to see how long the current conditions will last the service observer is deciding whichmix of observations will make the b est use of the site. In the same ro om an engineer is trouble-sho oting an o -line instrument via a video conference link to the Hilo base facility where the exp ert for this instrument is currently working. They compare notes, decide that it is the same problem xed earlier this month on Mauna Kea, and transfer the patch le. A few hours later as the system op erator is running through the nightly calibrations of the telescop e pointing and image quality the system op erator for Mauna Kea starts up a video link. She is having problems with the M1 supp ort system and wants to consult. While the Cerro Pachon telescop e automati- cally runs through its calibration pro cedure the two system op erators decide that it is the active actuator system whichmay b e causing the problem. As the Cerro Pachon system op erator has b een through this pro cedure b efore he logs in to the Mauna Kea M1 supp ort system using an engineering display and has a detailed lo ok at the actuators' p erformance. Isolating it to a particular actuator which is misb ehaving he advises the Mauna Kea system op erator how to turn a particular supp ort actuator o . The Mauna Kea system op erator do es so and then logs the problem in a distributed problem rep orting system that will b e used the next dayby the day crew to repair or replace the actuator. Other author information: Email: [email protected]; Telephone: 520-318-8429; Fax: 520-318-8590 Managed by the Asso ciation of Universities for Research in Astronomy,Inc.(AURA) under co op erative agreement with the National Science Foundation As the service observer is starting an infrared sp ectroscopic observation of a remote galaxy it b ecomes obvious that there is something p eculiar ab out its emission lines. The service observer decides that this is worth calling the principal investigator in Cambridge, England ab out and then do es so. After a brief teleconference discussing the di erent asp ects of the sp ectrum the PI decides to log on to the system remotely and lo ok at the sp ectrum himself. The next observation is listed as classical remote observing and the observer has b een waiting patiently in Tucson, Arizona to connect to the system and observe. She dials up the Gemini ISDN numb er and establishes a TCP/IP connection to the site, giving her control of the science op erations. As she works the telescop e up dates a video image of the guide eld as well as allowing her to interact via a full screen X window display, identical to that available on site. At the same time a video link allows her to interact with b oth the system op erator and the service observer. The ultimate goal for the communications system is to not b e noticed. It oughttowork so well that it is taken for granted, allowing users and supp ort sta to go ab out their tasks. Achieving this will require extensive planning and a lot of hard work. 2. COMMUNICATION CHALLENGES There are manychallenges facing us as we nalize the design of the communications system and b egin to implement it. Perhaps the most familiar challenge is cost. As with virtually any publicly-funded pro ject, Gemini must op erate with a limited budget. Money must b e sp ent wisely and choices accounted for. Confounding this is the rapid progress in electronics and communications services. For almost every asp ect of the communications work package, one could exp ect a signi cant price reduction in twoyears. New technologies are b eing develop ed and deployed at a dizzying pace. All of this makes the design of the communications system a delicate balance b etween what we can a ord, what we need now, and what we exp ect to happ en in the future. Another challenge is geography. Both telescop es are in remote lo cations with inhospitable climates. Access to the sites is a ma jor obstacle. Both Hawaii and Chile have limited access to services and equipment whichistaken for granted in the mainland USA. The distance b etween the base and summit facilities as well as the altitude of the summit facilities (14,000 feet at Mauna Kea, 9,000 feet at Cerro Pachon) makes work at the summit dicult. And of course the distance b etween Hawaii and Chile provides a great challenge. The lo cal infrastructure (or lack thereof ) p oses another challenge. Cerro Pachon is a remote p eak in the Chilean Andes. All access to and construction on the site has b een initiated for the Gemini Pro ject. In this case, the challenge also provides us the opp ortunitytobypass generations of old technology and install mo dern, proven equipment. In Hawaii, the telecommunications infrastructure lags far b ehind the mainland. Progress is b eing made, alb eit sometimes at a frustrating pace. Finally,therapid pace of change p oses an enormous challenge. Asynchronous Transfer Mo de (ATM) networks are evolving and standards are b eing prop osed, adopted, and sup erseded. Gigabit Ethernet is nearing standard- ization, and pro ducts are b eginning to app ear. Once proprietary video conferencing systems are moving towards standardization and even op eration over TCP/IP networks. Telephone switches are b eing intro duced which replace the traditional desktop handset with a p ersonal computer. Peering into the crystal ball of the future of technology is a daunting task. 3. USER REQUIREMENTS 2 An extensive list of user requirements has b een develop ed. This includes a number of communications areas: Data networking Telephone systems Video conferencing Public address systems Video monitoring systems Mobile communications systems Although this list is not all-inclusive, it do es cover the ma jor subsystems. Some of the requirements for these subsystems are discussed in the following sections. 3.1. Data networking Data networking is a broad category, including both the lo cal area networks (LANs) and the wide area networks (WANs). The data network is the single most imp ortant comp onent of the communications system { if the computers can not access the network, the telescop e can not op erate. There are some common characteristics for all our networks. All networks are required to carry TCP/IP trac; there is no requirement to supp ort other proto cols such as IPX, DECNET or AppleTalk. All LANs are required to op erate at a minimum of 10 megabits p er second (Mbps). All comp onents of the system should b e sp eci ed such that inevitable upgrades are relatively simple. 3.1.1. Summit network The network con gurations for Mauna Kea and Cerro Pachon will be as similar as p ossible; currently they have identical designs. The summit network consists of four separate LANs: the Control LAN, the Data LAN, the User LAN and the Technician LAN. The Control LAN is used for transmitting command, control and status trac amongst the real-time systems 3 which op erate the observatory. These are mostly VME computers running EPICS. Due to hardware constraints, this LAN will initially op erate at 10 Mbps. Trac volume on this LAN is exp ected to be mo derate, but latency should b e kept at a minimum. The Data LAN is used for bulk data transp ort.