Biospherical Instruments Inc.
Your Source for Optical Sensing and Aquatic Profiling Technologies

C-OPS: Compact Optical Profiling System
WHAT IS C-OPS?
C-OPS is a radiometer system for determining apparent optical properties in the ocean. It consistsof two radiometers: one measuring in-water upwelling radiance, and the other either downward
irradiance or upward irradiance. Both radiometers are equipped with 19 wavebands and are mounted
on a free-fall frame. The frame can be optimized for either slow descent rates for work in very shallow
coastal waters, or faster descent rates for observations in the open ocean. Available accessories
include above-water reference irradiance sensors to measure incident irradiance, the “BioShade”
shadowband assembly for making diffuse measurements, and the “BioGPS” for providing position
and time.

C-OPS
IrradianceCollector

WHY C-OPS?

Radiance
Instrument

In-water legacy systems are not always well suited for properly resolving the optical complexityof shallow waters, principally because of overall
instrument size, proximity of the sampling platform, or rate of descent. C-OPS does not haveany of these problems.

WHAT’S DIFFERENT ABOUT C-OPS?
•Ideal for both ocean color, and satellite
calibration and validation, in shallow water•Complete, integrated system for measuring
radiometric variables in coastal waters withsubmersible and above-water instrumentation (for both turbid coastal and clear oceanicwaters)•

Submersible instruments are optimized formeasuring vertical profiles of radiance andirradiance at depth

C-OPS is so lightweight it can be hand deployed,so the system can be operated from either small •or large vessels. In addition, its free-fall systemprecludes any influence from the shadow of theship.
••

It features rapid sampling (15 Hz); slow, freefall descent; adjustable buoyancy; it is hand
deployed; and has a 300 m maximum depth
Based on microradiometer technology
Developed in partnership with NASA

Biospherical Instruments Inc.
Microradiometers
The heart of the new C-OPS profiling system, and all of its accessories, is the microradiometer—a revolutionary new approach to photodetector integration.
The Biospherical Instruments Researchand Development Group has perfecteda miniature, stand-alone photodetector
called the “microradiometer.” The microradiometer consists of a filtered photodiodewith a microprocessor, a preamplifier with
controllable gain, a 24-bit analog-to-digitalconverter, and a serial port—all on one small
circuit board assembly the size of a pen. The
brass outer sleeve provides support andisolation from electronic noise.

Although every microradiometer is an independently
functioning photodetector, multiple microradiometers
can be clustered together to form multiple wavelength
radiometers. Aggregator assemblies (left) are used
to bundle clusters of microradiometers with auxiliary
sensors. Aggregators control the data flow to and frommicroradiometers. Aggregators also feature power
conditioning; additional sensors including tilt angles,temperature, input voltage and current; and onboard
removable data storage for specialized applications(microSD).

A cluster of 19 microradiometers
in a pressure housing, allied toan aggregator assembly (above)
forms a stand-alone multichannel
radiance ocean color sensor thatis small enough to hold in one
hand (right).

Your Source for Optical Sensing and Aquatic Profiling Technologies

Biospherical Instruments Inc.
C-OPS
The C-OPS near-surface buoyancy iseasily adjustable using a combinationof air filled and rigid foam floats. As thesystem descends, the increasing waterpressure compresses air-filled bladders,which reduces buoyancy and increases
the descent rate from <3 cm s-1 at the-1
surface, to over 30 cm s below 10 m.

The above-water reference sensor measuresincident global irradiance. Optional accessories include shadow band for measurementsof diffuse irradiance to support atmosphericcorrection schemes (BioShade), and GPS
integration for position and time (BioGPS).

The battery-powered master aggregator deckbox, the “Microradiometer Master Controller,”provides power and telemetry to a Windowsbased laptop computer (supplied), or otherPC. Biospherical Instruments custom software
is provided. The deckbox also contains an output port controller, which allows both the surface reference and in-water sensors to adapt
to different cable lengths, while supplying
optimum power to the sensors. The deckbox
displays an inventory of attached sensors on
power up, which is helpful in troubleshooting
cable and connection problems in complicatedshipboard environments.
Your Source for Optical Sensing and Aquatic Profiling Technologies

C-OPS Microradiometer Based Sensor Specifications
Each microradiometer contains its own complete control and acquisition system composed of a microprocessor, 24-bit analog-to-digitalconverter (ADC), voltage reference, temperature sensor, and electrometer front end. The electrometer is configured with three gains
controlling the conversion of current to voltage. A collection of microradiometers, typically sampling different wavelengths, is aggregated into a microradiometer cluster, or instrument, where an electronics package (“aggregator”) controls polling and acquisition ofsignals from each of the microradiometers. All microradiometers are synchronized to ensure simultaneous sampling at all wavelengths.
The aggregator also contains the power conditioning circuitry and data communications interfaces, and may also be equipped withinternal data storage (microSD Card—1 gigabyte) to support remote data logging.

Specifications
Microradiometer Specifications:

Microradiometer Power: ± 5 VDC at 4 mA total.

Detectors: Si (13 mm2), InGaAs (7 mm2), or GaAsP (7 mm2)

Optical Filters: 10 nm full width at half maximum multicavity iondeposited interference filters selected for greatest out-of-band blocking
and minimum fluorescence and maximum long term stability

Photocurrent-to-Voltage Conversion: Electrometer amplifier with threegain stages—1, 200, and 40,000.
ADC: 24-bit bipolar: 4–125 Hz data rates.
Dynamic Range (usable): 9 decades
Linearity: Measured on all microradiometers over a signal current range-12-5of 1 x 10 to 1 x 10 A using a programmable light source. Typically,errors are < 1% compared to a reference system electrometer. Gain ratios
are individually measured using a computer controlled optical source andprogrammed into each microradiometer.

Spectral Range: 250–1650 nm. (Range of 1100–1650 nm requires
InGaAs detectors.)

C-OPS Assembly Specifications:
Cluster Sizes: Microradiometers are assembled into collections of 13
and 19 wavebands in a single housing. The following applies to 19channel sensors:

Speed: ADC sample rate is programmable from 4–125 Hz, and is normally set to 125 Hz, with averaging over the sampling period performedinternally by the microradiometer.

Diameter: 2.75 inches

Response Time: Exponential change with a time constant of < 0.01 s.
Time required for gain change is < 0.1 s.

Wavelength Selection: Wavelengths are selectable from 250–1650 nm

Electronic Sensitivity: ADC resolution is 0.5 μV with a current resolutionof < 10-15 A. The saturation current is 160 μA. The 3-gain signal-range is
1.6 x 1011, defined as the saturation signal divided by minimum resolvablesignal.
Noise: Si detector typically has 15–20 fA of noise when ADC is samplingat 125 Hz with the internal microradiometer averaging of 25 samples, resulting in a data rate of 5 Hz.
Optical Sensitivity: Sensitivity depends on the spectral region andthe entrance optics (irradiance or radiance). It is expressed as Noise
Equivalent Signals at 5 Hz for radiance (μW cm-2 nm-1 sr-1) and irradiance(μW cm-2 nm-1):
ChannelRadiance

Irradiance

320 nm2.9x10-6

9.0x10-5395 nm5.0x10-6

6.9x10-5490 nm

1.8x10-6

2.3x10-5

683 nm9.9x10-7

1.1x10-5780 nm-7

8.0x10-6

6.8x10Note: Radiance is adjusted for
immersion in water. Note alsothat radiance sensors may bepointed directly at the solar disk
without saturating.

Dark Offsets: Dark offsets are measured and set at the time of calibrationfor each gain level. Offsets can also be automatically measured andapplied in the field to accommodate different temperature regimes.

Depth: 125 m maximum depth rating standard; 300 m versions areavailable.
Speed: A single, 19-waveband optical instrument can be operated at
rates greater than 30 Hz. Complete systems composed of three 19waveband radiometers can operate at rates greater than 15 Hz.
Data Rate: Optical instruments communicate at 115,200 baud, using
RS232 or RS485 (full or half duplex). Deck box communicates at 115,200
baud using RS232.
Power Requirements: Optical instrument with 19 channels: 7.5 V at
90 mA. Three instrument system, 19 wavebands, 0.30 A typical at thedeckbox.
Field-of-view Radiance Instrument: 7° half-angle in water (SeaWiFSspecification)
Cosine Error Irradiance Instrument: ± 3% for zenith angles smaller than60°; ± 5% for zenith angles 60–70°, and ± 10% for zenith angles from70–80°.
Free-fall Speed: < 1 cm depth resolution; adjustable terminal velocity
6 cm to 35 cm s-1; manually adjustable pitch and roll
Ancillary Sensors: Water temperature, water pressure transducers, andpitch and roll.

Available Accessories:
BioShade: Marine shadowband accessory for surface irradiancereference sensor.
BioGPS: GPS accessory; custom adaptable free-fall frames; individualcharacterizations.
Custom cable lengths, cable reels, and shipping containers. Details
available upon request.

Copyright ©2009 Biospherical Instruments Inc. Specifications subject to change without notice.

Your Source for Optical Sensing and Aquatic Profiling Technologies