NPL Calibrated Radiance Sphere (Labsphere 12" Dynamic Helios Range)

Maintaining a traceable calibration of our instruments is vital for both the field and airborne measurements. The uniform radiance sphere source is the ideal tool for the calibration and characterisation of multi and hyperspectral imaging instruments and from this, we can calculate measurement uncertainty.

Developments in sensor design have improved the data quality of images in the shortwave infrared region. Parallel to this has been the improvement in the performance of radiance spheres in the SWIR region by replacing the traditional barium sulphate coating with a thick PTFE (Spectralon) inner lining.

Through the development of the GHOST (Greenhouse Observations of the Stratosphere and Troposphere) project the National Centre for Earth Observation together with the Field Spectroscopy Facility have purchased and calibrated the new Helios radiance sphere system from LabSphere.

Available to loan for system calibration or cross calibration NERC science projects at FSF or user's laboratory.



Labsphere Helios Radiance Source Radiance Sphere Comparison Test
The new NCEO Helios radiance sphere.       Radiance spheres testing & calibration at NERC Airborne Research Facility, Cambridge

Features

High reflectance Spectralon (PTFE) inner liner for improved shortwave infrared spectral output in comparison to barium sulphate coating.

Highly uniform output when viewing rear hemisphere (back wall) or across output port.

Three tungsten halogen light sources for fixed or variable output from 0 to > 45,000 cd/m2 ( > 1.5 mW/m2/sr/nm @ 900nm)

NPL (National Physical Laboratory) spectral radiance calibration (350 - 2500 nm).

Robust cage design for greater portability.

Automated logging of all sphere parameters.

Specification

NPL Calibrated Spectral Range (75W lamp only):
350-2500 nm
NPL Certificate 2016020157-RB1-17
Spectral calibration is available for other radiance levels
Uncertainty:
350 - 450nm from 2.7 to 4.1%
450 - 2400nm from 1.7 to 3.8%
2400 - 2500nm from 5.1 to 12.3%
Dimensions:
sphere internal diameter: 285mm (11.2")
output port diameter: 100mm
Light Sources:
35W tungsten halogen - internally mounted
75W tungsten halogen - internally mounted
150W tungsten halogen - externally mounted with variable attenuator
Light Output Monitor
TE temperature stabilised photopic detector (data logged via PC)
Photometric (Luminance) Output Levels:
35W lamp only - 10,380 cd/m2
75W lamp only - 24,970 cd/m2
150W lamp only - adjustable from 0 to 9,960 cd/m2
Power Supplies:
Three independent precision current stabilised power supplies
Computer control ensure soft start and logging of lamp burn time
Control Software Application:
Full remote control.
Software logging includes lamp parameters - voltage, current and accumulated burn time
Photometer signal displayed, plotted and logged to database

Spectral Radiance Values (75W lamp only)

NPL calibration Values & uncertainty

Example Applications

  • Hyperspectral Image Sensor Calibration
  • Camera Flat Field Calibration & Characterisation
  • Radiance Calibration of Field Spectroradiometers & Ocean Color Radiometers
  • Linearity, Stability & S:N Measurements
  • Resources

  • Contact FSF for further information including the User Manual and spectral radiance files.