Throughout the next few weeks, we will be featuring a series of blog articles based off a presentation by ASD’s Co-founder and Chief Scientist, Dr. Alexander F. H. Goetz. The content was presented at the symposium associated with the celebration of the 10th anniversary of the launch of the EO-1 mission, held at the Goddard Spaceflight Center on November, 30 - December 2, 2010.
Field spectroscopy has evolved dramatically in the past 35 years. To understand what the future holds for scientific measurements, it’s important to understand how the field has developed over the past and what tools hold the most potential for supporting scientific advancement.
Over the next four posts, we plan to address:
- An overview of changes in field spectroscopy
- Product developments of early spectrometers
- Ruggedizing field spectroscopy instrumentation
- Future prospects in field spectral measurement
Part 1: An Overview of Changes in Field Spectroscopy
In the early 1970’s, a new era of digital data collection and storage dawned making way for new instrumentation advancements. The ability to gather and store data digitally truly made field spectroscopy feasible.
Electronics have changed most dynamically over the years. Because of these changes, instruments have gone from being bulky, extremely heavy units to convenient, portable hand-held devices. The transition from analog to digital saw devices go from huge masses of hardwired components to microprocessors. Years later, those microprocessors would become software in even smaller FPGA chips.
Additionally, electronic data storage underwent many developments. Paper chart recorders gave way to analog storage eclipsed by the advent of digital tape. From laptops to direct memory access to Ethernet to flash drives, field spectroscopy has adopted new technology at every turn.
Along with the changes in electronics, batteries have also benefited from advancement. Lead-acid batteries were standard in the early days. The freedom to explore the field using a reliable power supply yielded endless opportunities. In the end though, because of their bulk and low energy-to-weight ratio, lead-acid batteries did better in cars than as instrument components. Ni-Ag batteries were used for a while and were replaced with Ni-Cd and then NiMH batteries, each bringing new benefits and lower costs to field spectroscopy. Finally, Li-ion won out as the most popular and desirable battery. As found in all portable consumer electronics now, these lightweight, rechargeable batteries do provide the highest power density of all their predecessors.
Optics for field spectroscopy moved from the circular variable filter to the diffraction grating – both moving and fixed. The sophistication of today’s aberration-corrected, concave holographic gratings would have astonished Joseph Fraunhofer, the developer of the first practical diffraction grating way back in the early 1800’s.
Most significantly, detector developments allowed for superior field instruments in the 2000-2500nm region. Moving from PbS single detectors to arrays, to a Si PDA and finally toward extended-red InGaAs detectors was critical to collecting the highest-quality data in field research.
Technological innovations and developments in field spectroscopy increased the potential for better quality data over the years. Next week we’ll explore the early models of field instruments.