Robert Herlien

Measurement of sea surface partial pressure of C02 from a moored buoy

Abstract An autonomous analytical system for measuring the difference in partial pressure of CO 2 between the sea surface and the atmosphere was constructed and deployed on a buoy moored off the central coast of California. The apparatus was based on the conventional analytical techniques of sea surface gas equilibrium and non-dispersive infrared spectrometry. Hourly data were collected for a 70 day period in the winter-spring of 1993. Internal and shipboard calibrations indicate that an accuracy of 1–2 μatm was achieved and that long-term instrument drift was minimal.

A Device for Protecting Moored Spectroradiometers from Biofouling

A shutter mechanism for reducing the effects of biofouling on bio-optical instruments deployed on oceanographic moorings has been designed, built, and tested. The initial development was carried out on a spectroradiometer. The optics of the spectroradiometer are protected by copper shutters that rotate out of the field of view prior to a measurement and rotate back after the measurement is completed. The shutter system can sense an obstruction and, if one is detected, attempt to rotate in the opposite direction. The controlling software stores the home position in the memory so the shutter can return to cover the optics, irrespective of direction of rotation. The system has been tested in the equatorial Pacific, where it has provided five months of data that are unaffected by biofouling.

An ocean observatory sensor network application

We describe our implementation of a novel deep ocean sensor network, the MBARI Free Ocean CO2 Enrichment (FOCE). FOCE is a system designed for installation in the deep ocean to enable manipulative experiments that explore the impact of deep ocean increase in CO2 and resulting pH change on ocean biogeochemistry and ecology. This system uses control feedback and pH sensors to inject CO2 into a small volume of seawater, thus creating a controlled environment per science requirements. To implement this system, we utilized the MBARI-developed network middleware known as “SIAM”, which provides a standardized interface to instruments on a sensor network. For the FOCE application we integrated Open Source DataTurbine (OSDT) into SIAM. OSDT provides asynchronous communication links between distributed components, and is particularly well-suited to streaming instrument data. Combined with the existing synchronous SIAM framework, these features enabled a straightforward and efficient architecture for our application. We describe how we achieved our goals of software reuse of infrastructure and instrument services, instrument-in-the-loop control, and rapid assembly of a scalable end-to-end sensor network system.

Observatory Middleware Framework (OMF)

Large observatory projects (such as the Large Synoptic Sky Telescope (LSST), the Ocean Observatories Initiative (OOI), the National Ecological Observatory Network (NEON), and the Water and Environmental Research System (WATERS)) are poised to provide independent, national-scale in-situ and remote sensing cyberinfrastructures to gather and publish “community”-sensed data and generate synthesized products for their respective research communities. However, because a common observatory management middleware does not yet exist, each is building its own customized mechanism to generate and publish both derived and raw data to its own constituents, resulting in inefficiency and unnecessary redundancy of effort, as well as proving problematic for the efficient aggregation of sensor data from different observatories. The Observatory Middleware Framework (OMF) presented here is a prototype of a generalized middleware framework intended to reduce duplication of functionality across observatories. OMF is currently being validated through a series of bench tests and through pilot implementations to be deployed on the Monterey Ocean Observing System (MOOS) and Monterey Accelerated Research System (MARS) observatories, culminating in a demonstration of a multi-observatory use case scenario. While our current efforts are in collaboration with the ocean research community, we look for opportunities to pilot test capabilities in other observatory domains.

Satellite Link Management for an Ocean Observing Network

The Monterey ocean observing system (MOOS) moored observatory hosts tens of instruments on multiple networked nodes distributed over the sea surface, water column, and seafloor. Commands and data are exchanged between instrument nodes over high-speed copper and fiber-optic links at 10 Megabits per second using TCP-IP protocols. Science and engineering instruments on each node acquire and log data at various rates; the current deployment of five instrument nodes logs tens of Megabytes of data per day. Approximately 5 Megabytes per day of telemetry is required to provide a subset of science data and system status information. The surface node periodically establishes a PPP connection to shore using the Globalstar satellite system, providing a link for remote system control, maintenance, and telemetry retrieval Telemetry retrieval is particularly challenging, given the capacity and cost of the 7800 bits per second communications link. The challenge is compounded by limited satellite availability, wave-driven motion of the surface buoy antenna, and occasional outages of hard-wired network connections between nodes. To address these issues, we have developed software strategies to manage the low- bandwidth satellite link in a highly efficient manner. Elements of our telemetry retrieval strategy include use of data summarization algorithms, PPP compression, multi-threaded utilization of the satellite link, optimized data packet size to reduce protocol overhead, and assertive reconnection of prematurely disconnected satellite links. We discuss the efficiency and trade-offs of various approaches, as well as overall observed improvements in telemetry rates. Our current implementation is capable of retrieving at least 10 Megabytes of telemetry per day, and we discuss further improvements which could substantially increase that rate.