Specifications

1
SECTION 1.0
INTRODUCTION – a personal history by Gerald Persha
The SSP-4 IR photometer has a long history at Optec. In 1984 a prototype unit was first
designed and constructed using an uncooled Lead-Sulfide photoconductive cell from
Hamamatsu. The system used a chopper to stabilize the temperature drift and allow for
long integration times. Considering the available electronics and IR detectors at the time,
this instrument held much promise for small observatories attempting JHK photometry.
The prototype instrument was first demonstrated to an interested group of astronomers
and amateurs on the night of August 17, 1984 at the James C. Veen Observatory. The
event was the culmination of a symposium on “Near-IR and Solid-State Photometry”
hosted by Russell Genet and myself as part of the I.A.P.P.P. organizational and
educational efforts. The name of the observed star escapes me but a signal was detected
to the amazement and joy of all in attendance. Unfortunately, the joy was short lived as
the arm flailing of my soon to be ex-wife knocked a can of coke into the electronic works
of the instrument bringing the demonstration to a sticky and bitter end. Events in the
development of new computer controlled telescopes, photometers and visibility related
instruments directed the efforts of Optec into other areas for the rest of 80s and 90s and
the SSP-4 was shelved.
Since Optec had already developed the models SSP-1, 2 and 3 photometers, it was natural
to name this instrument the SSP-4. The SSP-5 and 7 were years away from development
and the defunct SSP-6 is a story for another time. Since 1984, the SSP-4 project notebook
and prototype remains had sat undisturbed on a crypt-like shelf at Optec.
Seventeen years later in August of 2001, I received a communication from Dr. Douglas
West about his desire to have an IR photometer manufactured. At first I dismissed it but
his persistence, knowledge of new detectors pertaining to the subject and this lingering
unfinished business in my life made me reconsider this photometer. Through his efforts in
organizing a serious group of astronomers both amateur and professional, a new and
improved SSP-4 photometer was proposed and designed using new technology and
detectors.
The relatively new InGaAs PIN photodiodes on the market were designed for the fiber
optics communication market and have reached very high performance levels compared
to the IR detectors of 1984. It is now possible to build an IR photometer, which will allow
a great many stars to be observed accurately in the J (1250nm) and H (1650nm) bands.
Unfortunately however, the characteristics of the detector material do not allow the K
band at 2200nm to be observed.
Without the hindrance from my ex-wife, the new SSP-4 was developed, tested, and
finally brought to market. The sequence of SSPs is nearly complete. Enjoy.