Our first flight for 2016 was on Saturday, April 23rd. It was an evening flight and the first test for our NITELITE project. For those of you who don’t know, NITELITE is the precursor mission to our more comprehensive and integrated NITESat (Nighttime Imaging & Tracking Experiment Satellite) mission to measure and characterize light pollution over the Midwestern United States from orbit, with special focus on Chicago and its environs (though we may also try to take data during passes of opportunity over other regions, including possibly outside the U.S., depending on our orbit and some other factors, such as our ability to capture data on demand). NITELITE is our first-round effort to design and test an imaging system that, though it will not be the exact same imaging system we expect to use on the satellite, will be comparable in terms of operation and specs, such as the camera control system and data handling.
The primary goals of this first test flight were:
- First run of the NITELITE Test Imaging System
- Test run of the FH OBC (On-Board Computer)
- Test run of the Live Video Transmission System
(If you want to know more detail about the systems we were testing, click the corresponding link above to jump ahead.)
We met at the Adler at 4 PM, loaded up all the flight gear (except the 30-foot pole – a crucial, but not fatal, oversight, which we are not likely to repeat any time in the near future). We pulled out of the Adler parking lot a full 2 minutes ahead of schedule at 4:58. A great start to a great evening!
Per our usual, we all headed for Koerner Aviation airport in Kankakee, IL (about an hour’s drive), to set up for launch. Not per our usual, we set up the balloon outside the hangar, because the hangar was too full of airplanes. (Cool!) No problem, the winds were nice and light, so everything went smoothly.
While at Koerner, Lou and Colton confirmed an open comm channel for them to use, then they headed to Kankakee Community College to set up the directional antenna on the roof for the live video transmission test.
We launched the balloon at about 7:30 PM, right on schedule, then piled into our vehicles (1 van + 2 cars) and began the chase. Andrew and his students, who were in the trailing car, ran into a bit of a snag, due to one of the car’s headlights being out (a whole story unto itself), but they not only managed to catch up with the rest of us, they were also the first to spot the payload after it landed — in a tree. (Here’s where the 30-foot pole would have come in handy. But, to quote Ken, who is (1) Polish and (2) working on getting his tree climber certification, “Who needs a 30-foot pole when you have a Pole who can climb 30 feet!”) Thanks to Ken, we were able to retrieve the payload without incident.
To our great delight, all three of the main systems we were testing gave some good results. So, our first NITELITE test flight was a rousing success! We are looking forward to our next NITELITE test flight, which will be another evening flight. Stay tuned!
NITELITE Test Imaging System
The initial test imaging system that we flew on April 23rd consisted of a hacked Canon SX130 IS camera and an Arduino. The camera used a CHDK script that we controlled with a simple on-off switch through the USB. For our next NITELITE test flight, which is scheduled for May 28th, we will try to use a Raspberry Pi, instead of the Arduino.
Far Horizons On-Board Computer (OBC)
The OBC is based on an Arduino Due. It is connected to our IMU and Copernicus II GPS systems via standard two-wire serial ports. It receives GPS sentences every 4 seconds and IMU information at a 5 Hz rate.
The OBC is programmed very simply, with an inner loop that processes GPS and IMU serial port bytes into an internal sentence buffer. When the sentence buffer is complete, as signaled by a flag byte, the sentence is parsed and the most recent “state” (GPS and IMU) information is accordingly updated and time-stamped with the current internal clock. Every 5 seconds the state information is written to a log file on an SD card. Every 300 seconds a trigger sentence is written to the camera subsystem via a third serial port. This also triggers a write out of the camera sentence and state information to the log file. The whole system is powered by two lithium 9 volt batteries and installed in a “standard” tray.
Live Video Transmission System (LVTS)
Our LVTS consists of a GoPro camera, a simple transmitter, a directional antenna, a receiver, a signal converter, and a video streaming device. (And, of course, YouTube.)
On the balloon payload: The GoPro camera puts out an analog TV signal, which is fed into a miniature (2.5-Watt) analog TV transmitter. The transmitter’s antenna broadcasts video continuously on a single channel @ 1258 MHz, which is an amateur radio band (i.e., Amateur Television or “ATV”).
On the ground: A special highly directional antenna (similar to the old Yagi TV antennas) is mounted on a tripod. The antenna is connected to a small TV receiver that’s designed for the specific frequency of the transmitter’s signal (channel). The receiver reproduces the transmitter’s analog TV signal and feeds it into a converter, which converts it to the modern HDMI digital format (important for streaming). The signal is then sent to a video streaming device, which converts the signal into an internet data stream that goes directly live to YouTube. (We use a popular brand of video streaming device that’s commonly used by gamers to record or live stream their gaming prowess, so their fans can watch and admire.) Though not a required component of the LVTS, an HDMI monitor can also be connected, so the folks on the ground can see what the GoPro is seeing.
The antenna must be pointed with reasonable accuracy toward the signal source (i.e., the transmitter on the balloon). Since it has no automatic controls to point it at the balloon, the antenna must be manually aimed by looking at the balloon track on aprs.fi and estimating in what direction and at what angle upward to point the antenna, so that it is aimed toward the balloon (basically, an educated guess).
For our April 23rd flight, Lou and Colton set up the antenna on a rooftop at Kankakee Community College, with enthusiastic assistance from staff at the College, coordinated by Rob Kenney. The College is roughly 5 miles away from Koerner Aviation airport, where we launch our balloons. They had their hands full with the setup and manual pointing of the antenna, so they didn’t get a chance to take photos of their setup, but here’s an earlier pic of the antenna.
The altitude and angle of the balloon were changing rapidly during the flight while the balloon was within relatively close range of the antenna, so it was a challenge to point the antenna during that part of the balloon track. However, after the balloon got further away, the flight path was less variable and the angle from the antenna to the balloon stayed almost constant, so it didn’t require as much adjustment to keep the antenna pointed. There seemed to be some interference, though, possibly from the local Wi-Fi at the College, and/or from the Greater Kankakee Airport, which was nearby and has quite a bit of high-powered radio, including radar, which could interfere with reception. The signal later faded out when the balloon reached ~50,000 feet altitude (~10 miles up) and ~30 miles away.
Overall, we were able to get some good footage, but unfortunately after the live stream finished the video was not archived on YouTube. We’ll try to rectify that next time, in addition to hopefully making some other improvements.