October 15, 2001
With so many flowers and so little time, life as a bee is not always as sweet as honey.
Fortunately, many flowers help these hard-working insects by showing them patterns that direct them to food sources. These patterns, however, are only visible in the ultraviolet range, something that many insects can detect. Humans, on the other hand, cannot see these signatures with the naked eye, but instead must use special equipment.
To the delight of scientists, technological progress at JPL has produced a high-performance chip that is capable of detecting very weak ultraviolet signals. This chip technology has increased sensitivity and robustness to the point that it could be used to explore distant planets.
Yet searching for life on distant planets was not the original goal of the scientists who developed this technology. A simple demonstration of a new camera containing the chip showed that the technology intended for ultraviolet astronomy could also detect ultraviolet signatures of Black-eyed Susan flowers, and gave researchers a glimpse of its potential for future applications in astrobiology.
"We had this sophisticated ultraviolet chip technology that we had used, for example, to image galaxies, and we wanted to set up a simple, indoor demonstration. This simple demonstration of a new technology may lead to exciting new applications in the search for life in the universe," said Dr. Shouleh Nikzad, researcher and head of the Nanoscience and Advanced Detector Arrays Group at JPL. "What may appear as a lifeless environment in visible light could come alive when seen in ultraviolet. This is an example of the vital part that technology plays in all sciences."
Using ultraviolet signatures to study the chemical composition and processes in celestial objects is nothing new. Ever since humans figured out a way to send spacecraft beyond Earth's atmosphere, ultraviolet astronomy has given scientists a new view.
But the key to flying this technology on a future spacecraft, in addition to its high performance, is its exceptional durability. The reason for its superior capacity to withstand the rigors of space flight is built into the tough silicon lattice of the chip. The camera uses the same charge-coupled device, or CCD chip, found in a regular camcorder, only modified to be sensitive to ultraviolet light. The chip response to light changes dramatically when a few layers of crystal silicon are added to the chip surface with a procedure called delta doping. The key to seeing the ultraviolet light is to control what happens to the electrons that are very near the surface of the chip. By building this control into the silicon crystal, JPL scientists created an extremely durable device.
"The camera is sturdy, just like a camcorder, and the chip technology is very durable. I keep the chip in my desk drawer; take it on the field, store it in the lab. It's extremely robust," Nikzad says as she handles the lightweight camera.
Stability is what some other devices that see in the ultraviolet lack. Those devices must work under tightly controlled conditions such as low temperatures, or must be in a vacuum, or they lose their sensitivity to ultraviolet photons almost immediately.
The chip's ability to see in ultraviolet is stunning. Compared to a similar imaging array on the Hubble Space Telescope, this chip is three to 10 times more efficient in detecting ultraviolet light, depending on the region of the spectrum.
Eventually, astronomers might make a beeline for this technology to help them study the cosmos.