been released from their P-POD
dispenser.
The current program in the
Model CubeSat waits in a loop for a
button to be pressed before
beginning its mission and releasing
the antenna. Eventually, I’ll find a
tactile switch with a longer
pushbutton that actually protrudes
from the bottom of the airframe. The
Model CubeSat will wait until it’s
lifted off the table to signal it’s been
dispensed from its P-POD. One other
thing I discovered about the power
plane is that the main power switch
must be replaced; it’s too difficult to
reach inside the airframe and flip on
the switch its currently using. I’ll
replace it with a pushbutton switch
with a plunger long enough to reach
the surface of the airframe.
Microcontroller Plane
The microcontroller plane
supports the PICAXE and I2C
memory chip. The memory allows
the Model CubeSat to store
science data until its next radio
contact with the ground station.
There are two changes I want to
make, however.
First is to shift the DB- 9
programming header outward just
a bit more. Right now, it’s just
beyond reach of the PC’s
programming cable. Then, on the
underside of the PCB, is a right
angle header for the deployables’
micro-servo. I want to move that
servo header to the power plane
in the next version.
Photometer Plane
Currently, the only science-related plane for the Model CubeSat
is a two-channel LED photometer.
This measures light intensity in the
blue and infrared portions of the
spectrum. A future upgrade will let
students select which two colors of
the spectrum to measure.
There are LED detectors at each
corner of the PCB in the hopes that
using many LEDs will make the
CubeSat less sensitive to pointing
direction. The plane also contains an
LM335 temperature sensor to
calibrate the LED’s output (LEDs are
sensitive to their temperature). The
photometer’s intensity readings
appear on a bus I/O as a variable
voltage where they are then digitized
by the microcontroller.
Radio Plane
The last plane is the radio
plane. It provides two-way
communication with a simulated
ground station. The radio is an
So, what about the ground
station? The ground station I’m using
was originally designed for a moon
August 2015 73
This microcontroller plane
contains a PICAXE-14M2.
Eventually, I'll switch to a
PICAXE-18M2 for access to
more I/O.
The first science-focused plane is the
photometer plane.
The XBee radio provides two-way
communication between the Model
Something borrowed,
something blue. This XBee
radio is from a moon rover
project I made using
CheapBots.
