Remote observing from the Keck Headquarters in Waimea, Hawaii, has been implemented for both Keck Telescopes. The network in use between Headquarters and the observatory on the summit of Mauna Kea has slowly evolved to its current form, a T-3 (45 Mbit/sec) fiber link. This bandwidth is more than sufficient to allow remote control of the instrument, image data downloading, and eavesdropping operations. The instrument control software is networked in the same way as for our remote satellite-based system: remote display of windows using X Window System protocols.
Every attempt has been made at Headquarters to emulate on-site observing at the telescope, including separate remote control rooms for each telescope, identical software environments, and astronomer quarters. A single T-1 of bandwidth is used by an advanced PictureTel videoconferencing system, which keeps the observers and OAs in video and audio contact for the entire night. Although a primary benefit of remote observing from California is not realized, namely the reduction of travel time and costs, the proximity of technical observatory staff and the freedom from altitude-related difficulties has made remote observing from Keck Headquarters a very popular mode of observing. As much as 75% of the observing in a given month currently takes place remotely at Headquarters (depending primarily on the complexity of the instrument being used).
A separate project has been undertaken by Bob Kibrick and others at the University of California Observatories (UCO/Lick) and Keck Observatory to enable remote observing from California over terrestrial networks. Initial experiments have used the Internet, with the eventual goal to acquire the necessary bandwidth in the form of a guaranteed-bandwidth leased line. The key to this project has been the decision to remove the instrument control interface to the remote computer, with only low-level command packets and image data packets being transferred over the network. This minimizes the traffic over the network, while enabling a quickly responding interface. This separation of the user interface from the underlying instrument control software has proved relatively easy to implement because of the modular construction of the Keck Telescope control system. Figure 11 illustrates that this separation of the ``observing control computer'' and the ``LRIS control computers'' already exists, and was in fact used to our advantage in the ACTS project as well, to create a separate remote observing control computer connected to the ATM network.
The other advantage to this approach is that it enables the large image data files to be transferred to the remote host while the instrument CCD is reading the data from the hardware itself. Since this operation currently takes one or two minutes with the LRIS instrument (depending on the instrument mode), the result is that the remote user will see exactly the same image ``read-out'' rate as the local user, provided that the bandwidth is at least 8 Mbytes per 60 seconds, or 1.1 Mbit/sec, less than a T-1. Although this is an instrument-specific number and the required bandwidth will certainly increase as instruments become more complex with larger detectors, this allows us to implement an initial remote observing system with little software or hardware expense. This remote observing technique was successfully demonstrated at the SPIE meeting in July of last year . A similar test in October has demonstrated the ability of this technique to multiplex several remote users at different locations, a capability of great benefit to large observing teams. We expect remote observing from the mainland U.S. to become increasingly common with Keck Observatory in the next few years.