Brightest Bird in the Sky: The RAVAN Satellite Set to Fly
Why put one satellite into orbit for 150 million dollars, when we could put up 40 for the same price? That is exactly what the Applied Physics Laboratory (APL) at Johns Hopkins University, NASA’s Earth Science Technology Office (ESTO), and Draper Lab proposed this week with the RAVAN project.
In 2015, the first RAVAN – Radiometer Assessment using Vertically Aligned Nanotubes – satellite will be launched. This represents a crucial step toward developing a dynamic model of global temperatures and climate change.
Simply put, climate change is believed to be the result of an imbalance between incoming and outgoing radiation. If the Earth’s radiation imbalance (ERI) is zero over time, the climate should trend towards a steady state. If ERI is positive, as we believe it to be, the climate will enter a state of increasing instability, with powerful weather events as a consequence. To understand and predict instability and future weather, we need to know the ERI.
Historically, high-precision measurements required to calculate the ERI accurately have been unattainable. “ERI is currently estimated using models, meteorological reanalysis, measurements of ocean heat content, and satellite measurements,” reported RAVAN Principle Investigator Dr. Bill Swartz from APL, “past and current satellites do not have the accuracy needed to definitively define ERI. There are still assumptions that have to be made.”
Those assumptions center around how much heat the Earth itself is radiating back into space. "We have systems in place to monitor the radiation coming in from the Sun to better than half a watt per square meter,” explained Dr. Lars Dyrud, Project Lead. “We have never tried to measure the absolute amount of outgoing radiation from the Earth." Likening ERI to a bank account balance, Dr. Dyrud summed up the reason RAVAN was born, "we’ve never measured that final balance."
Not knowing the absolute amount of outgoing energy has prevented us from calculating the total energy of Earth’s atmosphere. This in turn prevents us from developing accurate models of climate change-models that would allow us to draw connections between global temperature and phenomena like hurricanes and El Niño.
Enter ESTO’s RAVAN. Its measurements of radiation emitted by the atmosphere would allow us to finally solve the energy equation. The ensuing models of excess energy would be mechanisms for predicting weather patterns and global warming.
Global weather modeling is a big achievement for a tiny object. Only 10 x 10 x 30 centimeters in size, RAVAN is an example of a cubesat. Cubesats, also known as microsatellites, are so-called because they are about the size and shape of a shoebox. Each satellite weighs less than a car battery, solar panels included.
Cubesats like RAVAN accomplish major scientific feats with minimal hardware. Magnets used for guidance double as orbital stabilizers. This reduces fuel needs. To boost transmission capacity, RAVAN will bounce signals bound for Earth off its solar panels. The bulk of RAVAN’s payload is comprised by a single detector about the size of a deck of cards. These innovations keep the cubsat trim as well as efficient.
In addition to being small and smart, RAVAN is designed to be highly durable in space and supremely sensitive to outbound radiation. The secret to this success in both areas is RAVAN’s main instrument: bundles of carbon nanotubes bound together to create a radiometer.
Carbon nanotubes are, according to Dyrud, "by far the blackest and most uniformly black substance known to human kind." Their uniform color and surface boosts the sensitivity of the sensor to previously unknown levels. With their small size, the carbon nanotubes stand up brilliantly to temperature variations experienced in orbit. As an added bonus, nanotubes are easily grown in a lab, facilitating satellite assembly.
Decreases in complexity and size allow ESTO to put dozens upon dozens of cubesats into space. For what had been the cost of single satellite, we can have a fleet of cubesats like RAVAN.
Individually, and as part of a collective, cubesats like RAVAN promise us a far greater understanding of our world than we presently possess. With each low-cost microsatellite making high-precision measurements, a fleet of RAVAN cubesats could paint a 3D picture of global temperature output, for the first time, in realtime.
“A constellation of [RAVAN cubesats] would allow for unprecedented measurements of the outgoing radiation and the Earth radiation imbalance, which would allow for better tuning of models, a better understanding of Earth’s radiation budget, and a better prediction of future climate,” concluded Schwartz.
While RAVAN may be the first of its kind in terms of guiding us toward a greater understanding of climate change, a larger revolution in microsatellites has already begun.
Days before RAVAN was announced to the world, 29 cubesats were launched into orbit on a single Minotaur rocket. Two were cubesats from APL. Eight were educational cubesats representing six universities, West Point, and Thomas Jefferson high school in Alexandria, VA. This event set a record for simultaneous satellite deployment, and was only possible due to the new microsatellite design that RAVAN espouses and will take to the next level in 2015.
Cubesats, or microsats, represent a critical restructuring of space-based science experimentation. "Until you ask someone to make a cell phone small enough to fit into your pocket, they won’t do it," Dyrud explained.
The trend toward tiny, sleek and accessible has transformed Earth technologies. Computational machines that took up any entire buildings now fit into a billfold. Orbiting observation platforms have evolved similarly. We have witnessed their transformation from single-use, individually-designed, costly endeavors to instruments even a high school can possess. The day is not far off when satellites will be mass-produced: smart, small, suited to a single purpose. ESTO’s RAVAN will migrate through the skies setting such an example.
It won’t be long before others come flocking.
The RAVAN project is funded by ESTO, Johns Hopkins APL, Draper Lab, and L-1 Standards and Technology.