Please Note: SkyCube re-entered the Earth's atmosphere on 9 November 2014. We are maintining this legacy page as a resource for the CubeSat community.
SkyCube is a 1U CubeSat. CubeSats are a new kind of nano-satellite, made possible by advances in microelectronics over the past decade. The first CubeSats were developed at Stanford and Cal Poly universities in 1999, and launched in 2003. As of mid-2013, over 150 CubeSats have flown into orbit.
CubeSats are tiny, fitting into standard rectangular frames. The smallest "1U" frames, like SkyCube's, are simply a cube 10 centimeters on a side. Larger 2U and 3U CubeSats are common, with frames that are double or triple the 1U length.
CubeSats are piggybacked into orbit along with much larger satellites. Because the vast majority of the launch costs are borne by the primary satellite, piggybacking a CubeSat into orbit is much less expensive than a dedicated satellite launch. CubeSats missions are thus affordable to university programs and small companies.
SkyCube's launch service providers, responsible for manifesting the satellite aboard the Orbital Sciences Antares rocket and deploying it from the International Space Station, are Spaceflight Services, Inc. and Nanoracks, LLC. We reccommend both launch providers for future small satellite projects.
Because SkyCube is so small, its solar power budget is very limited. At any one time, only half of the satellite is illuminated by sunlight. And for half of each orbit, the entire satellite is in darkness. SkyCube uses very efficient solar cells to compensate, but still only produces about 4 watts of solar power on average. Its electronics are therefore engineered for very lower power consumption.
SkyCube contains a main computer board, a radio and antenna, solar panels, a rechargeable Li-ion battery pack, and a set of three wide-field, VGA-resolution cameras. The satellite has a passive magnetic stabilization system, consisting of permanent magnets attached to the 1U frame. These align the satellite into a stable orientation with respect to the Earth's magnetic field. SkyCube's radio, computer, and power system were devloped by Astronautical Development, LLC - a pioneering CubeSat hardware vendor whose radios have flown on more CubeSats than any other. All of SkyCube's electronics utilize the Texas Instruments MSP430 microcontroller, which has has a long and successful flight heritage on other CubeSat misions. SkyCube's onboard control software was developed by senior firmware engineer Chris Phoenix of Southern Stars.
SkyCube's solar panels and their deployment system were designed jointly by AstroDev and Southern Stars, using high-efficiency Spectrolab Triangular Advanced Solar Cells, produced by Boeing for low-cost space applications. SkyCube's lithium-ion batteries are MoliCell ICR18650J cells qualified for use aboard the International Space Station, and kindly supplied to us by ABSL Space Products in Longmont, CO.
SkyCube's cameras utilize Micron Technology's MT9V011 image sensor and VIMicro's VC0706 digital video processor. Both are commonly used in camera modules for industrial and outdoor security applications. We added improved lenses from Edmund Optics, with panoramic, human-eye, and high-resolution fields of view of 120°, 35°, and 6°, respectively. The high-resolution camera has a minimum ground sample distance of 135 meters - roughly the size of a city block. The National Oceanic and Atmospheric Administration (NOAA) issued a commercial earth-sensing license for SkyCube on 31 January 2013.
SkyCube will broadcast from space at a frequency of 915 MHz, and listen for commands from the ground on 450 MHz. To communicate with the satellite, Southern Stars has partnered with the US Navy, to use a brand new high-bandwidth CubeSat ground station network. This Mobile CubeSat Command and Control (MC3) network provides data downlink rates up to 57.6 kbps - six times faster than most other CubeSat missions. This lets SkyCube transmit a large number of images from space. MC3 ground stations are located in Honolulu, HI; Monterey, CA; Logan, UT; and Dayton, OH. Additionally, we have partnered with Saber Astronautics to use an additional ground station in Sydney, Australia.
As with many other CubeSats, radio transmissions from SkyCube will be detectable by anyone with inexpensive amateur radio equipment. The Federal Communications Commission (FCC) granted an experimental broadcast license for SkyCube on 1 April 2013. SkyCube's call sign is WG9XMF. Your "tweets from space" are simply SkyCube's beaconing pings, modulated with 120 bytes each of message data from our project sponsors. SkyCube will broadcast one ping every 10 seconds when it's not communicating with a ground station. Here are some of our favorite "tweets from space", submitted by sponsors from our Kickstarter campaign:
Your "tweets" can be anything consistent with the educational nature of the mission. They can be a story, divided into 120-character chunks. They can be scheduled consecutively, or dispersed throughout the mission. We will provide amateur radio equipment capable of detecting SkyCube's transmissions to our $1000-and-higher sponsors. And we'll also give SkyCube its own twitter feed, so you won't need anything more than a web browser or smart phone to follow along.
The empty gray box shown at the top of the satellite model above is the container that holds SkyCube's balloon. We will command the ballon to inflate 90 days into the mission.
Most CubeSats are far too small to see from the ground, but SkyCube will be an exception. The satellite will carry a tightly-packed balloon, made of 0.35-mil (9 µm) low-density polyethylene, coated with highly reflective titanium dioxide (TiO2) powder. During the final phase of the mission, the balloon will be inflated with a 4-gram CO2 cartridge, and expand to a diameter of nearly 7 feet (2 m). This will make SkyCube brightly visible to millions of people on the ground as it passes over the Earth's twilight regions.
SkyCube's balloon serves another purpose. Once it inflates, SkyCube's orbit will decay rapidly due to atmospheric drag. Less than two weeks after balloon inflation, SkyCube will re-enter the Earth's atmosphere and burn up harmlessly. The balloon lets SkyCube end its mission cleanly, and avoid becoming space debris that could harmfully impact future missions. SkyCube's balloon was developed by Global Western, an experienced supplier of aerostats for NASA, JPL, and others with unique high-altitude ballooning needs.
Further details are available in SkyCube's Orbital Debris Assesment Report (ODAR), required by NASA and approved with our FCC license, above.