Chips in Space: Let’s look inside ARISSat-1

Chips in Space: Let’s look inside ARISSat-1 (Part 3)

Welcome to my third and final chapter on the ARISSat-1’s subsystems, which covers all of the Cs:  communications, cameras, control and cabling, along with the university experiment that hitched a ride. Next week’s blog post will begin a discussion of the challenges we encountered while designing the satellite—and how we solved them—followed in later posts by a summary of the lessons learned from ARISSat-1’s deployment and operation.

ARISSat-1 has been in operation for three weeks, now. The most up-to-date status information can be read at http://www.arissat1.org/v3/ and the AMSAT Bulletin Board. The battery is surely dead. ARISSat-1 orbits the Earth every 90 minutes. On each orbit, when it enters eclipse, no power is generated by the solar panels and the systems effectively reset. Otherwise, operations continue to be nominal.

Let’s finish up the description of the subsystems…

Interior View of the Receiver RF PCB

RF
The RF module has a 2-meter-band communications transmitter for the downlink, and produces a total of 500 milliwatts of power. The input to the downlink transmitter is a 10.7 MHz intermediate frequency (IF) signal that is generated by the Software Defined Transponder (SDX). (See Part 1 for more info on the SDX.)The RF module also has a 70-centimeter-band communications receiver, and its output is a 10.7 MHz IF signal that is fed to the SDX.

Concept Drawing Showing the 2-meter Antenna at Top and 70-cm Antenna at Bottom

Antennas
There are two antennas. The 2-meter downlink antenna is mounted to the top, and the 70-cm uplink antenna is mounted to the bottom. As mentioned in my deployment update blog of August 3, 2011, the 70-cm antenna appears to be broken off in the video of the deployment. We may never know what happened to that antenna, but to our pleasant surprise, radio amateurs are still able to communicate with ARISSat-1 just fine using 1 Watt on the uplink.

Interior view of the camera module

CamerasWe used Hunt Electronics’ HTC-2N3 Series CCD Sensor type cameras. There are four cameras, each pointing in a different axis.  If you take a look at the ARISS SSTV Gallery site, note that the call sign RS01S is in four different colors:

•    Red: -Y pointing camera, side view, mirror reverses image
•    Green: +Z pointing camera, top view (you can see the tip of the 2-meter antenna)
•    Blue: -Z pointing camera, bottom view
•    Magenta: +Y pointing camera, side view, mirror reverses image

The output is NTSC video that is digitized by the four-channel video input processor on the Internal Housekeeping Unit (IHU), which was also discussed in Part 1.

Exterior view of control panel

Control panel
The control panel allowed the cosmonauts to activate the satellite. It is an important component of the safety system. Upon flipping the three toggle switches, power was applied to the satellite and the safety timers were enabled, giving the cosmonauts 16 minutes to safely deploy the satellite before it started transmitting.

One of the First Pictures ARISSat-1 Took (captured by Mike Rupprecht, DK3WN)

Once ARISSat-1 was powered up, it started taking pictures. Two of the photos captured the cosmonauts handling the satellite. Here’s one that was captured by Mike Rupprecht, DK3WN, of Germany.

Photo of the Kursk University experiment

Kursk experiment
To the right of the control panel on the top plate is the Kursk science experiment. This experiment was developed by students at the Kursk State University in Russia, and is intended to measure the vacuum of space. The experiment was started 30 minutes after deployment, and will run once each day for a complete orbit. Telemetry from the experiment is transmitted on the downlink.

Interior View of ARISSat-1 Showing the Cabling

Cabling
No satellite is complete without cabling. Cables are something that you wish to minimize because they are not easy to assemble, are very labor intensive and take a long time to assemble. They are also prone to vibration failures, if not carefully laced with connectors secured in place. The cable harness was handmade. Individual strands of insulated wire and connectors were assembled according to the length of the cable run and the placement of the connectors. This makes for a nice, neat installation. It also facilitates the cable-harness tie downs, which keep the cable harness in place.