Background



As a result of a request from Goonhilly Earth Station Ltd., the Heritage Society took up designing a new activity for a “Women in Engineering Day” event at a Truro School, to encourage girls to think of a career in the Sciences. To make it relevant, an activity was decided which links the early days of Satellite Communication to the new developments in Space with GES Ltd. In the early 1960’s much of the equipment used for the Satellite Communications were developed at Goonhilly, and the performance of the receiving system was measured by tracking reference Radio “Stars”, Cassiopeia A (Supernova Remnant), Taurus A (Messier Object M1 Supernova Remnant), and Cygnus A (a Radio Galaxy). Now the bigger antennas at Goonhilly could be going full circle, and again be used for Radio Astronomy or Space Mission communications, so we decided to create the Star Trekking Activity to link the old and new uses.



Making The Display



Design started with the idea of a simulation “Sky” populated with the evening constellations which students could relate to. Fortunately, we had just received a donated pop-up display frame which made a useful support for a magnetically attached corrugated cardboard sheet for the “Sky” backdrop. Also, we had received a drivable model dish antenna from the Martlesham Laboratories which could be quickly adapted to steer a Laser pointer fixed to the superstructure. A reference sky view for the time of the event was captured from the German DLR heavens-above.com web-site, and once trimmed appropriately, the Summer Sky Chart was projected onto the cardboard backdrop using a Computer Projector. The primary star positions of the constellations were then painted with white areas in preparation for masking with the stylised star shapes cut out from a printed sheet of paper and pinned onto the areas. To space-black the backdrop, the cardboard was taken outside and with a group effort the whole area was sprayed with black matt paint. After a short wait for the paint to dry in the Sun, all the star masks were removed leaving white star shapes in their correct positions.​



Robin With Paul B's Donated Pop-Up Frame



Proposed Target Backdrop



Paula, Simon, & Robin Marking Star Positions



Making "Star" Masks For Backdrop



Over-spraying Pinned Star Masks



Masks Removed To Leave Stars



Tony & Robin Checking Constellations Are OK



Paula Retouching Incomplete Stars



Trigger Plan For The Electronics



The Electronics



The aim of this activity is to light up “Stars” by pointing a Laser Pointer beam at sensors in trigger “Stars”, so electronics had to be made to achieve this, and control the functioning of it. The circuit chosen is a simple Set / Reset Latch logic circuit, four of which are in each package (CD4044BE), whilst interfacing to and from the backdrop “Stars” is made using small high gain buffer amplifier circuits (known as Darlington Drivers) in another integrated circuit (ULN2804A) where 8 of these could provide input buffering to the four Set inputs and outputs buffering for the four Latches. A simple external common button circuit was added to the control boards which connects to all the Latch Reset inputs so that the display can be cleared of any previous activity attempts for someone else to try. The two Control Boards were hand wired in high density configuration, making each board able to handle 16 circuits, giving plenty of circuits to activate. Even so, there were more “Stars” in the Constellations portrayed, so trigger “Stars” were configured with extension wiring to activate other nearby subordinate “Stars” in the Constellation at the same time. The actual “Stars” were activated with high brightness Light Emitting Diodes (LEDs) at their centres, with the limited colours available trying to be close to the real star colours. As the Constellations get illuminated, the scene becomes quite colourful, so on the event day there was something artistic in the activity to add to the sciences implication as well as providing a competitive side to see who could light the most stars in a time period. The activity was very popular during the day.





Basic Outline Of One Star Circuit



Single Circuit Connection To Control Board



PCB Layout For Hand Wiring



Control Board Being Wired



Control Board Connected To Backdrop Ccts



General View Of Completed Back Wiring



Final Additions



Time to create the activity was quite tight, so two additional items ran out of time to complete for 2017, but it was considered worth completing them afterwards as the activity was erected in the GHS Laboratories for other events. The idea was to provide two additional whimsical items to activate in blank areas on the backdrop, so a cut out of a Telstar satellite and a small green space alien “Arrie” in his pink flying saucer were developed. Both had active chaser images when targeted, using simple transistor circuits and rows of LEDs and would be activated in the same way as the “Stars”. Since completion, this activity proved popular with visiting education groups from the GES Ltd Summer Schools events as part of a number of support activities available at the GHS Labs.