Joe Demusz

Joseph N. Demusz joined the Anderson research group in June of 1981 as an Electrical Engineer. He quickly assumed the responsibilities of organizing the electronics lab and forming the design team structure that continues on to the present. Joe died on June 9th, 2011, leaving behind a long legacy of students, colleagues and friends. A few months before his death, Joe wrote the following description of his work in the Anderson Group:

Over the past almost thirty years Joe has been responsible for the design, fabrication, test, quality assurance and field support of all electrical and computer systems that comprise all laboratory, ground and airborne scientific instruments that this research group has produced. The airborne instruments include platforms such as high altitude balloons, unmanned aerial vehicles (UAVs), Satellites and  NASA's high altitude aircraft such as the ER2 (U2, R model) and WB-57.

During this time Joe has also been actively involved with teaching outside the research group. He has taught in the College of Engineering at Boston University. There he taught undergraduate courses in Digital Design, Electric Circuit Theory, Electronics and a graduate course in Modern Active Circuit Design. Additionally, Joe taught a three semester course in Electronic Design at Northeastern University. These teaching skills have been put to good use in our research group where Joe mentors graduate students, postdocs and other engineers in the fine points of electrical and electronic design.

The design, fabrication, testing and deployment of the class of instrument that our group builds requires minimally many months and and often years of focus and perseverance. Joe has always been the at vanguard of these efforts; that is, identifying the necessary design elements, measuring the efforts required, and then finding and allocating professional resources to get the job done. Throughout the years with his guidance and sometimes temerity, this research group has enjoyed a remarkable success rate for all the instruments produced.

Additionally, Joe has also produced many circuit designs to bring life to these many instruments. It would be impossible to list all his contributions, so what follows is a brief list of designs that were either a first, a one of a kind, or of particular note.

High Voltage Power Supply

This design was the first solid state design to achieve a power level greater than 2 kiloWatts. Its purpose was to power a copper vapor laser on a high altitude balloon. The laser needed 10 kiloVolt pulses at a 17 kiloHertz rate with an average power of 2.5 kiloWatts. Additionally it had to operate at an altitude of 130,000 feet and run of batteries for 4 hours.

Precision High Voltage Source

To precisely control the reverse voltage on an avalanche photodiode it was necessary to have an adjustment range of 1000 to 2000 Volts. Further, it had to be discernible in 20 milli Volt steps and stable to 20 parts per million. Since it would be used on high altitude aircraft, it also had to operate under wide temperature ranges and low pressure. Accuracy and stability here were unique and unprecedented.

Precision High Power Temperature Controller

To measure chlorine nitrate in the stratosphere, an instrument was developed that would fly aboard a NASA High Altitude ER-2 aircraft. Making this possible required  thermal dissociation of the chlorine nitrate molecule and the subsequent measurement of its constituents. A precision heater and controller was developed that used 4 kiloWatts to heat the airflow through a nacellle. Air temperature of the flow was then raised to 500 degrees centigrade and held stable to better than plus or minus 5 degrees. The controller was noteworthy in that it used pulse width modulation for control and dissipated less than 1% of the heat delivered. Nothing like this had ever been flown before.

High Sensitivity PreAmp

Company to any sensor is a preamp. Joe developed a preamplifier that would sit next to the aforementioned heater and detect very small signals using constant fraction discrimination. Detection sensitivity of the preamp was of the order of two to three hundred electrons. But, the fact that it achieved this, while sitting next to the pulse width modulated heater which is an impressive noise generator, demonstrated a triumph in the development of noise immune design.

Precision Temperature Measurement System 

Developed a methodology for a miniaturized multichannel system that measures temperature of a black body to within a millidegree.

Lastly, Joe has not only contributed to the design effort but has overseen the development of all phases of our data acquisition systems. He has brought them from a laborious mammoth hand-wired system to one that is miniaturized and employs components 4mm x 2mm in size that can be machine placed and sit on a twelve layer printed circuit board. This constant development exploring new technologies has made it possible to utilize new and diverse platforms in the pursuit of understanding atmospheric chemistry and climate change.