Fig. D: Nature plot compares
ozone measurements by TOPS and
Nimbus- 7. In 1992 the calibration of
the satellite’s instrument began to
drift. Fig. E: Scientist Brooke Walsh
measures the ozone layer with the
world-standard ozone instrument
at Hawaii’s Mauna Loa Observatory.
Fig. F: The ozone layer over South
Texas, measured by the author.
Red points from 1990 to 1994 were
measured by TOPS- 1. Blue points
from 1994 to 1997 were measured
by Microtops and Supertops. Points
from 1997 to 2010 were measured
by Microtops II, manufactured by
Goddard Space Flight Center (GSFC) about the discrepancy, they politely reminded me that the satellite
instrument was part of a major scientific program
and not a homemade instrument. I responded that
I had built a second TOPS and both showed a similar
difference, but this didn’t convince them.
During August of 1992, I visited Hawaii’s Mauna
Loa Observatory for the first time to calibrate my instruments at that pristine site 11,200 feet above the
Pacific Ocean. The world-standard ozone instrument
was also being calibrated there, and it indicated a
difference in ozone measurements made by Nimbus-
7 that were similar to what I had observed.
Eventually NASA announced that there was
indeed a drift in the calibration of its satellite ozone
instrument. A paper I wrote about this sparked my
career as a serious amateur scientist when it was
published in Nature, another leading science journal
(“Satellite Ozone Monitoring Error,” page 505, Feb.
11, 1993). Later GSFC invited me to give a seminar
The regular ozone measurements I began on
Feb. 4, 1990, have continued to this day along with
measurements made by various homemade instruments of the water vapor layer, haze, UVB, and other
parameters. In future columns we’ll explore how you
can also make such measurements — and very
possibly make discoveries of your own.
on my atmospheric measurements that they titled
“Doing Earth Science on a Shoestring Budget.” That
talk led to two GSFC-sponsored trips to study the
smoky atmosphere over Brazil during that country’s
annual burning season, and several trips to major
forest fires in western U.S. states.
Forrest M. Mims III (
forrestmims.org), an amateur scientist
and Rolex Award winner, was named by Discover magazine
as one of the “ 50 Best Brains in Science.” He edits The Citizen
28 Make: Volume