I take NASA's Science News email service. It is sometimes too consciously
anxious to drum up interest to hold my attention.
But this time, news of a hard X ray image from a balloon hoisted to
120,000 ft altitude caught my attention.
Here's an extract of the story:
Ramsey and his team used a replication technique to mass produce affordable
high-precision x-ray mirrors, which they can nest one inside another
to increase collecting area.
"We call the program High Energy Replicated Optics -- or HERO for short,"
says Ramsey.
The replication technique works like this: the mirror-builders electroplate
nickel alloy onto an aluminum mold polished in the shape of an x-ray mirror.
Next, they cool the nickel-coated mold. Aluminum contracts more than nickel,
so the nickel shell, in the form of a HERO mirror, slides right off.
Vacuum-coating the mirror with iridium, a dense metal that reflects x-rays
better than other substances, is the final step in the process.
Earlier this year the team assembled a prototype double-barreled x-ray
telescope consisting of two mirror assemblies with three shells each.
"Cosmic x-rays don't reach Earth's surface," explains Ramsey, "because
our atmosphere is opaque to this high energy radiation." It was time
to go to space -- or as near to it as they could get.
On May 23rd, the National Scientific Balloon Facility launched
the HERO team's innovative telescope from Fort Sumner, NM, on board
a helium-filled balloon. The payload ascended to 40 km altitude
(above 99.7 percent of Earth's atmosphere) where the sky is mostly
transparent to hard x-rays.
Each of the HERO mirror assemblies focused hard x-ray photons
from the Crab Nebula and Cygnus X-1 onto a spot seven-tenths of a
millimeter in diameter.
"Despite a collecting area of only 4 square centimeters," he says,
"the mirrors gathered plenty of photons from these sources.
We achieved almost the same sensitivity as a 1000-square centimeter
detector would with no focusing mirrors."
"Our mirrors weren't the only breakthrough," he added.
"We also developed an optical camera that can track stars down to
9th magnitude in broad daylight."