Located at the top of the Mauna Loa Strip Road, the HVO/RVTS-1 repeater site is conveniently accessible by car for servicing. The site consists of an encased FreeWaveTM transceiver connected to an omnidirectional antenna. The power station consists of a single 12V deep cycle battery, low capacity charge regular and a 50 watt solar panel (table 3)
A summary of equipment used at the HVO Receiver Site, along with general specifications, is presented in table 4. This site is the communication hub for the HVO/RVTS-1 . An omnidierectional antenna mounted outdoors at HVO serves a FreeWaveTM transceiver that is connected to a COM port of the receiver hub computer. A standard terminal emulator program on this computer is used to configure all in-line radio modems . A licensed HyperScanTM RX50S software package is used to communicate through the telemetry array with the remote site HyperScanTM TH50RX Digital Transmitter Module. The software is user friendly with mouse controlled pull-down menus and simple "point and click" access to all functions. The receiver software controls the reception, display, archiving and reviewing of digital images from the remote site. Options for labeling and time/date stamping of transmitted images are also controlled at the receiver hub. The computer is fitted with a serial-number-encoded HyperScanTM software key that is required for complete program operation. For a complete overview of software utilities, optional configurations, and detailed instructions for installation and operation, the reader is referred to the well-written equipment manual provided by HyperScanTM.
The communication link to the radio modem at the receiver site is handled by HyperScanTM as a null modem single-line link. Digital images transmitted and displayed and/or archived by HyperScanTM can be set for high, normal or low resolution. High resolution images are used for all remote camera sites and are transmitted at a rate of less than 4 seconds per frame. Incoming images can be viewed on the receiver hub monitor in multi- frame-/single-camera (time-lapsed mode), multi-frame/multi-camera, or single-frame/single-camera modes with either full screen or screen-plus-menu viewing options.
The system is set to store all "alarmed" images (described above) from each camera as transmitted over ~30 seconds at 5 minute intervals. The option exists to save every incoming image in the same time-coded image file as the "alarmed" images. The image review software allows playback of time coded image files in a moving picture mode with options for date and time selection, moving picture dwell-time, reverse playback, frame freezing and image capture to a clipboard file.
HVO/RVTS-1 experienced a HyperScanTM software upgrade from version 2.0 to version 2.1 in July 1997. The most significant change in software is a less restrictive proprietary format for image storage and review (v. 2.0 RDX file format changed to v. 2.1 DBF file format). The new image review program can be loaded on independent computer workstations (without a software key), allowing for convenient off-site image review and processing. The newer software is supplied with a database conversion utility that is only marginally effective at successful conversion of large HyperScanTM RDX image files to DBF formats. For this reason, and in order to view images collected from April through July 1997, the earlier version (v. 2.0) is preserved in a separate directory on the receiver hub computer.
Image files are stored in directories that are changed weekly in order to keep HyperScanTM image files archived in easily manageable sizes of less than 200 Mb. Establishing a new storage directory is a non-intuitive process not described in the instruction manual. A set of blank proprietary format files (files with suffixes of ".dbf", ".cdx", ".fil" and ".tre" in the HyperScanTM RX directory) are copied to a new directory on the storage drive and renamed with date-name prefixes. Before loading the new "date.dbf" file into the HyperScanTM software as a new "system default" database, the data transmission link must be interrupted. After the new default condition is set and the communication link is reestablished, the program will begin writing saved image files to the new database file. HyperScanTM image files are presently stored on a 9 GB hard drive partitioned into 2 GB sectors and thus accessible by LAN-linked DOS-or NT-based workstations for image review. Until a dedicated removable-media storage device is implemented, the files are backed-up via LAN-line to a high-capacity multi-user tape backup system at HVO.
The receiver hub computer is conveniently located where well-trained HVO staff are able to view the eruption conditions at a glance or complete a review of images in the active image directory. This multi-user environment is supported by the HyperScanTM software security package (password protected) which is invoked to prevent inadvertent access to system configuration and database maintenance privileges.
Three different camera configurations of two and three cameras have been positioned near the rim of Pu`u `O`o crater, viewing activity within and around the cone from April through September 1997. These sites and respective camera views are illustrated in figure 3. Two separate remote transmitter sites (sites A and C) were stationed on the north rim of Pu`u `O`o with views into the crater. An interim site on the south rim of the cone (site B) was used to monitor Episode 55 South Shield activity as well as that within the Pu`u `O`o crater. Site C was established when eruptive conditions threatened site B. A summary of Remote Camera equipment configurations and deployment intervals for each site is presented in table 5.
The following sections provide an overview of eruptive activity that is documented by the HVO/RVTS-1 image database. This information is presented to demonstrate the utility and value of this system and is not a complete eruption narrative. The reader is referred to the HVO USGS Website at http://www.hvo.usgs.gov for current eruption nomenclature and for a more complete narrative of recent eruptive history.
Deployed to observe ongoing eruptive activity within and near the Pu`u `O`o vent, HVO/RVTS-1 has documented the growth of the Episode 55 south shield area, the dramatic evolution of an intra-crater vent, and the cyclic rise and fall of lava within the crater. The system has captured a record of several Pu`u `O`o overflows that extended beyond the decimated west wall and spilled over one third of the crater's rim on the east side.
The Cannon MCC1 MKII camera was successfully deployed as Camera #2 on the north rim of Pu`u `O`o from April 12 through May 7, 1997. This camera was stationed with a westward view into the crater and positioned to observe a zone of consistent upwelling on the western margin of a circulating lava pond. At the time of deployment, the pond was exhibiting ~5 m depth fluctuations at a nominal depth of 50 to 60 m below a reference mark on the south rim of the crater. The real-time video record from this interval shows the gradual stagnation of the pond surface and the development of an isolated vent area on the west edge of the new crater floor. The camera recorded the early growth of a spatter cone and periodic surges of activity that produced short-lived intra-crater pahoehoe flows. This image database includes cessation of activity during an eruptive pause and documents the variations in style and vigor of crater-vent activity that can be correlated with concurrent eruptive activity of new vents on the flank of the Pu`u` O`o cone. Figure 4 depicts the "A2" remote camera site and sample images from the database for this interval.