INTRO PAGE
(1) WHAT YOU'LL NEED
(2) DOWNLOAD PARTS SHEETS
(3) ASSEMBLY INSTRUCTIONS
(4) ABOUT YOUR MODEL
About Your 1/250 Scale Model 34m BWG DSS
It is possible at all to replicate a 34m Beam Waveguide Deep Space Station (DSS) tracking antenna using paper only for
two reasons. The first reason is that the DSS's structure was designed to make optimum use of materials, minimizing
mass. This is because the whole thing has to move. Paper card stock provides good enough structural strength due to the
many triangles incorporated in the DSS design.
The second reason it works well in paper is that the waveguides that direct the path of microwave signals (both inbound to the receivers, and outbound to the spacecraft's receivers) are gigantic. And reproducing them in this paper model makes it clear, to one who builds or examines one, how this process works in principle.
The result is a scale model which rotates about axes in azimuth and elevation very much like the actual DSS. It incorporates the correct major structures, and articulating beam waveguides in their correct locations. It shows where two pairs of mirrors are located, and how they act as pairs of periscopes for microwave energy.
Of course there are many aspects of the real DSS that are approximated, or not represented at all, in your
model.
Mirrors
The all-important mirrors are not represented in this model. These are the large reflectors within the waveguide tubes aboveground and belowground, which direct microwave radio signals in and out of the basement equipment.
Anyone who examines or builds this scale model needs to imagine that there is a pair of diagonal mirrors (like an
optical periscope) within each of the two horizontal waveguide sections. The microwave beam is unbroken while the
reflector rotates in elevation, and while the whole assembly rotates in azimuth about the central descending
waveguide.
For those persons who are using this website to create a model much larger than the 1/250 size, for example in a science museum or college planetarium, consider using real optical mirrors, aligning them carefully, and letting them reflect a bright light from within the pedestal. Such a periscope would offer viewers proof of the concept of directing a beam between the communications equipment in the DSS basement and the main reflector (or at least the subreflector), as the reflector moves.
The image at left shows the mirror inside the beam waveguide that corresponds to the outboard section of model parts
labelled "UPPER PERISCOPE."
Additional Differences
The DSS's main reflector has a parabolic surface inside, which of course your model's main reflector does not have. The structure that supports the DSS's main reflector does indeed, though, have on its outside, generally the shape of the printed graphics outside your model's reflector.
The DSS has platforms which are not represented in your model. One platform holds the elevation motor. Another at the top of the alidade provides access to the elevation bearing and the upper waveguides.
Stairways, ladders, and railings are not represented.
Your model permits the reflector to go too far over backwards in elevation. Normal travel is from about 0° elevation (pointing to the horizon) up to around 90° (pointing straight up).
How to Track an Interplanetary Spacecraft
Set the main reflector to the "stow" position, pointing straight up.
This is the position the DSS normally takes during the "pre-calibration" period, for example an hour, before the DSS is scheduled to begin tracking its designated spacecraft.
During "precal" as it's called, all the equipment in the basement of the DSS, and in the Signal Processing Center (SPC) located some distance away, are prepared for the tracking assignment. Frequencies are set. Measurements of the exact distance from the SPC to the DSS are checked. Systems are calibrated and made ready.
Rotate the reflector down all the way in elevation.
At the same time, rotate the whole assembly in azimuth until the reflector is pointing toward a point on the eastern horizon.
Wait for a spacecraft to rise.
When Jupiter rises above the eastern horizon, the Galileo spacecraft, in orbit about Jupiter, is in view and its signal can be received. When Saturn rises, the Cassini spacecraft will be rising soon, too. (After July 1, 2004, Saturn will have moved east in its solar orbit enough to capture the arriving Cassini/Huygens spacecraft in its gravity, where the spacecraft will orbit during the rest of its lifetime.) When Mars rises, more spacecraft come into view.
Follow that spacecraft!
For the assigned tracking period, the DSS constantly moves its main reflector in azimuth and elevation to keep signals from the spacecraft beaming down its pair of microwave periscopes, into the equipment in the DSS's basement. Normally, the subreflector is constantly making small motions of its own, keeping the signals in focus.
At an agreed time, a transmitter, also in the basement, may be turned on. Its beam of microwave radio energy, guided by the beam waveguide mirrors, travels out at the speed of light, eventually to reach the spacecraft. It takes around an hour and a half to reach Saturn. It takes over twelve hours to reach Voyager 1.
Send Data to JPL.
All during the DSS's tracking period, which is normally planned weeks or months in advance during iterative negotiations within the user community, signals from the DSS travel to the SPC as "baseband" signals. There, in the SPC's equipment, they become binary digits, bits, of data. The data are forwarded to JPL in Pasadena, and then stored and distributed as needed to the user, for example the Cassini Program. Commands may also be sent from the user, through the SPC and DSS, out to the spacecraft. Monitor data, such as the DSS's azimuth, elevation, and other measurements, are also sent to JPL during the assigned tracking period.
Get a new assignment.
At the agreed time, for example after the spacecraft has traversed the entire sky, and is setting on the western horizon, the DSS completes its tracking. Transmitters are turned off. The reflector points straight up to the stow position. Everything is made ready for a new assignment, for example to track another spacecraft that will be rising soon, or participation in a radio astronomy observation, or in a radar astronomy experiment. Perhaps it's time for a few hours of maintenance work, or the installation of new sensitive equipment in the basement.
DSS-55 - The Movie
Visit the DSN Video Gallery where you can select a time-lapse movie that shows the entire project of constructing DSS-55 at Madrid in just a few minutes. You can also select "The DSN Story," another informative movie.
Beam Wave of the Future
The three venerable giant, 70-meter aperture DSSs, one each at Goldstone, Madrid, and Canberra, are the world's best at gathering low-level signals from spacecraft, and transmitting powerful uplinks across vast interplanetary distances.
It is possible for four 34m BWG DSSs to track one spacecraft, and feed their
signals into special combining equipment in the SPC, to create the equivalent of one 70m DSS. It is likely that additional
installations of 34m BWG DSSs will continue over the years, to help satisfy the need need for additional DSN tracking
capability, demanded by a growing user community.
Click below to build your 34m BWG DSS 1/250 Scale Model.
INTRO PAGE
(1) WHAT YOU'LL NEED
(2) DOWNLOAD PARTS SHEETS
(3) ASSEMBLY INSTRUCTIONS
(4) ABOUT YOUR MODEL
