When Oumuamua, the first interstellar object ever observed passing through the Solar System, was discovered in 2017, it exhibited some unexpected properties that left astronomers scratching their heads. Its elongated shape, lack of a coma, and the fact that it changed its trajectory were all surprising, leading to several competing theories about its origin: was it a hydrogen iceberg exhibiting outgassing, or maybe an extraterrestrial solar sail (sorry folks, not likely) on a deep-space journey? We may never know the answer, because Oumuamua was moving too fast, and was observed too late, to get a good look.
It may be too late for Oumuamua, but we could be ready for the next strange interstellar visitor if we wanted to. A spacecraft could be designed and built to catch such an object at a moment’s notice. The idea of an interstellar interceptor like this has been floated by various experts, and funding to study such a concept has even been granted through NASA’s Innovative Advanced Concepts (NIAC) program. But how exactly would such an interceptor work?
A new nanosat has been quietly snapping over 4500 pictures of the Earth and the sky after its launch on May 15th. Rocketed into orbit on a Falcon 9, the nanosat, known as GEOStare2, actually contains two different telescopes – one focuses on a wide field of view while the other has a much narrower field of view but much higher resolution. Together they aim to provide data on Earth, the stars, and the network of satellites in between.
Novel propulsion systems for CubeSats have been on an innovative tear of late. UT has reported on propulsion systems that use everything from solid iodine to the Earth’s own magnetic field as a way of moving a small spacecraft. Now there is a potential solution using a much more mundane material for a propellant – water.
Student-led teams aren’t the only ones testing out novel electric propulsion techniques recently. Back in November, a company called Exotrail successfully tested a completely new kind of electric propulsion system in space – a small hall-effect thruster.
Staying afloat in space can be deceptively hard. Just ask the characters from Gravity, or any number of the hundreds of small satellites that fall into the atmosphere in a given year. Any object placed in low Earth orbit (LEO) must constantly fight against the drag caused by the small number of air molecules that make it up to that height.
Usually they counteract this force by using small amounts of propellant. However, smaller satellites don’t have the luxury of enough propellant to keep them afloat for any period of time. But now a team of students from the University of Michigan has launched a prototype satellite that attempts to stay afloat using a novel technique – magnetism.
On June 25th, 2019, The Planetary Society‘s cubesat spacecraft known as LightSail 2 lifted off from the NASA Kennedy Space Center in Florida aboard a Falcon Heavy rocket. This was the second solar sail launched the Society, the first (LightSail 1) having been sent into space in 2015. Like its predecessor, the purpose of this spacecraft is to demonstrate the technology that would allow for solar sails operating within Low Earth Orbit (LEO).
Since reaching orbit, the LightSail 2 has been indicated that it is in good working order, as indicated by the Mission Control Dashboard recently introduced by The Planetary Society. In addition to establishing two-way communications with mission controllers and passing a battery of checkouts, the spacecraft also took its first pictures of Earth (and some selfies for good measure).
The RainCube 6U CubeSat with fully-deployed antenna. Credit: NASA/JPL-Caltech
Weather tracking is difficult work, and has historically relied on satellites that are large and cost millions of dollars to launch into space. And with the threat of climate change making things like tropical storms, tornadoes and other weather events more violent around the world today, people are increasingly reliant on early warnings and real-time monitoring.
However, NASA is looking to change that by deploying a new breed of weather satellite that takes advantage of recent advances in miniaturization. This class of satellite is known as the RainCube (Radar in CubeSat), which uses experimental technology to see storms by detecting rain and snow using very small and sophisticated instruments.
The first image captured by one of NASA's Mars Cube One (MarCO) CubeSats. The image, which shows both the CubeSat's unfolded high-gain antenna at right and the Earth and its moon in the center, was acquired by MarCO-B on May 9. Credit: NASA/JPL-Caltech
In 1990, the Voyager 1spaceprobe took a picture of Earth when it was about 6.4 billion km (4 billion mi) away. In this image, known as the “pale blue dot“, Earth and the Moon appeared as mere points of light because of the sheer distance involved. Nevertheless, it remains an iconic photo that not only showed our world from space, but also set long-distance record.
As it turns out, NASA set another long-distance record for CubeSats last week (on May. 8th, 2018) when a pair of small satellites called Mars Cube One (MarCO) reached a distance of 1 million km (621,371 mi) from Earth. On the following day, one of the CubeSats (MarCO-B, aka. “Wall-E”) used its fisheye camera to take its own “pale blue dot” photo of the Earth-Moon system.
The two CubeSats were launched on May 5th along with the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander, which is currently on its way to Mars to explore the planet’s interior structure. As the first CubeSats to fly to deep pace, the purpose of the MarCO mission is to demonstrate if CubeSats are capable of acting as a relay with long-distance spacecraft.
An artist’s rendering of the twin Mars Cube One (MarCO) spacecraft as they fly through deep space. Credit: NASA/JPL-Caltech
To this end, the probes will be responsible for monitoring InSight as it makes its landing on Mars in late November, 2018. The photo of Earth and the Moon was taken as part of the process used by the engineering team to confirm that the spacecraft’s high-gain antenna unfolded properly. As Andy Klesh, MarCO’s chief engineer at NASA’s Jet Propulsion Laboratory, indicated in a recent NASA press release:
“Consider it our homage to Voyager. CubeSats have never gone this far into space before, so it’s a big milestone. Both our CubeSats are healthy and functioning properly. We’re looking forward to seeing them travel even farther.”
This technology demonstration, and the long-distance record recently set by MarCO satellites, provides a good indication of just how far CubeSats have come in the past few years. Originally, CubeSats were developed to teach university students about satellites, but have since become a major commercial technology. In addition to providing vast amounts of data, they have proven to be a cost-effective alternative to larger, multi-million dollar satellites.
The MarCO CubeSats will be there when the InSight lander accomplishes the most difficult part of its mission, which is entering Mars’ extremely thin atmosphere (which makes landings extremely challenging). As the lander travels to Mars, MarCO-A and B will travel along behind it and (should they make it all the way to Mars) radio back data about InSight as it enters the atmosphere and descends to the planet’s surface.
Artist’s interpretation of the InSight mission on the ground on Mars. Credit: NASA
The job of acting as a data relay will fall to NASA’s Mars Reconnaissance Orbiter (MRO), which has been in orbit of Mars since 2006. However, the MarCOs will also be monitoring InSight to see if future missions will be capable of bringing their own relay to Mars, rather than having to rely on an orbiter that is already there. They may also demonstrate a number of experimental technologies, which includes their radio and propulsion systems.
The main attraction though, are the high-gain antennas which will be providing information on InSights’ progress. At the moment, the team has received early confirmation that the antennas have successfully deployed, but they will continue to test them in the weeks ahead. If all goes according to plan, the MarCOs could demonstrate the ability of CubeSats to act not only as relays, but also their ability to gather information on other planets.
In other words, if the MarCOs are able to make it to Mars and track InSight’s progress, NASA and other agencies may contemplate mounting full-scale missions using CubeSats – sending them to the Moon, Mars, or even beyond. Later this month, the MarCOs will attempt their first trajectory correction maneuvers, which will be the first such maneuver are performed by CubeSats.
In the meantime, be sure to check out this video of the MarCO mission, courtesy of NASA 360:
The cloud-enshrouded Venus appears featureless, as shown in this image taken by NASA’s MESSENGER mission. In ultraviolet, however, the planet takes on a completely different appearance as seen below. Credits: NASA
From space, Venus looks like a big, opaque ball. Thanks to its extremely dense atmosphere, which is primarily composed of carbon dioxide and nitrogen, it is impossible to view the surface using conventional methods. As a result, little was learned about its surface until the 20th century, thanks to development of radar, spectroscopic and ultraviolet survey techniques.
Interestingly enough, when viewed in the ultraviolet band, Venus looks like a striped ball, with dark and light areas mingling next to one another. For decades, scientists have theorized that this is due to the presence of some kind of material in Venus’ cloud tops that absorbs light in the ultraviolet wavelength. In the coming years, NASA plans to send a CubeSat mission to Venus in the hopes of solving this enduring mystery.
The mission, known as the CubeSat UV Experiment (CUVE), recently received funding from the Planetary Science Deep Space SmallSat Studies (PSDS3) program, which is headquartered as NASA’s Goddard Space Flight Center. Once deployed, CUVE will determine the composition, chemistry, dynamics, and radiative transfer of Venus’ atmosphere using ultraviolet-sensitive instruments and a new carbon-nanotube light-gathering mirror.
Ultraviolet image of Venus taken by NASA’s Pioneer-Venus Orbiter in 1979, lending Venus a striped, light and dark appearance. Credit: NASA
The mission is being led by Valeria Cottini, a researcher from the University of Maryland who is also CUVE’s Principle Investigator (PI). In March of this year, NASA’s PSDS3 program selected it as one of 10 other studies designed to develop mission concepts using small satellites to investigate Venus, Earth’s moon, asteroids, Mars and the outer planets.
Venus is of particular interest to scientists, given the difficulties of exploring its thick and hazardous atmosphere. Despite the of NASA and other space agencies, what is causing the absorption of ultra-violet radiation in the planet’s cloud tops remains a mystery. In the past, observations have shown that half the solar energy the planet receives is absorbed in the ultraviolet band by the upper layer of its atmosphere – the level where sulfuric-acid clouds exist.
Other wavelengths are scattered or reflected into space, which is what gives the planet its yellowish, featureless appearance. Many theories have been advanced to explain the absorption of UV light, which include the possibility that an absorber is being transported from deeper in Venus’ atmosphere by convective processes. Once it reaches the cloud tops, this material would be dispersed by local winds, creating the streaky pattern of absorption.
The bright areas are therefore thought to correspond to regions that do not contain the absorber, while the dark areas do. As Cottini indicated in a recent NASA press release, a CubeSat mission would be ideal for investigating these possibilities:
“Since the maximum absorption of solar energy by Venus occurs in the ultraviolet, determining the nature, concentration, and distribution of the unknown absorber is fundamental. This is a highly-focused mission – perfect for a CubeSat application.”
CubeSats being deployed from the International Space Station during Expedition 47. Image: NASA
Such a mission would leverage recent improvements in miniaturization, which have allowed for the creation of smaller, box-sized satellites that can do the same jobs as larger ones. For its mission, CUVE would rely on a miniaturized ultraviolet camera and a miniature spectrometer (allowing for analysis of the atmosphere in multiple wavelengths) as well as miniaturized navigation, electronics, and flight software.
Another key component of the CUVE mission is the carbon nanotube mirror, which is part of a miniature telescope the team is hoping to include. This mirror, which was developed by Peter Chen (a contractor at NASA Goddard), is made by pouring a mixture of epoxy and carbon nanotubes into a mold. This mold is then heated to cure and harden the epoxy, and the mirror is coated with a reflective material of aluminum and silicon dioxide.
In addition to being lightweight and highly stable, this type of mirror is relatively easy to produce. Unlike conventional lenses, it does not require polishing (an expensive and time-consuming process) to remain effective. As Cottini indicated, these and other developments in CubeSat technology could facilitate low-cost missions capable of piggy-backing on existing missions throughout the Solar System.
“CUVE is a targeted mission, with a dedicated science payload and a compact bus to maximize flight opportunities such as a ride-share with another mission to Venus or to a different target,” she said. “CUVE would complement past, current, and future Venus missions and provide great science return at lower cost.”
A cubesat structure, 1U in size. Credit: Wikipedia Commons/Svobodat
The team anticipates that in the coming years, the probe will be sent to Venus as part of a larger mission’s secondary payload. Once it reaches Venus, it will be launched and assume a polar orbit around the planet. They estimate that it would take CUVE one-and-a-half years to reach its destination, and the probe would gather data for a period of about six months.
If successful, this mission could pave the way for other low-cost, lightweight satellites that are deployed to other Solar bodies as part of a larger exploration mission. Cottini and her colleagues will also be presenting their proposal for the CUVE satellite and mission at the 2017 European Planetary Science Congress, which is being held from September 17th – 22nd in Riga, Latvia.
NanoRacks CubeSats photographed after deployment from the ISS by an Expedition 38 crew member. Credit: NASA
One of the defining characteristics of the modern era of space exploration is the open nature of it. In the past, space was a frontier that was accessible only to two federal space agencies – NASA and the Soviet space program. But thanks to the emergence of new technologies and cost-cutting measures, the private sector is now capable of providing their own launch services.
In addition, academic institutions and small countries are now capable of building their own satellites for the purposes of conducting atmospheric research, making observations of Earth, and testing new space technologies. It’s what is known as the CubeSat, a miniaturized satellite that is allowing for cost-effective space research.
Structure and Design:
Also known as nanosatellites, CubeSats are built to standard dimensions of 10 x 10 x 11 cm (1 U) and are shaped like cubes (hence the name). They are scalable, coming in versions that measure 1U, 2Us, 3Us, or 6Us on a side, and typically weigh less than 1.33 kg (3 lbs) per U. CubSats of 3Us or more are the largest, being composed of three units stacked lengthwise with a cylinder encasing them all.
A cubesat structure, 1U in size, without the outer skin. Credit: Wikipedia Commons/Svobodat
In recent years larger CubeSat platforms have been proposed, which include a 12U model (20 x 20 x 30 cm or 24 x 24 x 36 cm), that would extend the capabilities of CubeSats beyond academic research and testing new technologies, incorporating more complex science and national defense goals.
The main reason for miniaturizing satellites is to reduce the cost of deployment, and because they can be deployed in the excess capacity of a launch vehicle. This reduces the risks associated with missions where additional cargo has to be piggybacked to the launcher, and also allows for cargo changes on short notice.
They can also be made using commercial off-the-shelf (COTS) electronics components, which makes them comparably easy to create. Since CubeSats missions are often made to very Low Earth Orbits (LEO), and experience atmospheric reentry after just days or weeks, radiation can largely be ignored and standard consumer-grade electronics may be used.
CubeSats are built from four specific types of aluminum alloy to ensure that they have the same coefficient of thermal expansion as the launch vehicle. The satellites are also coated with a protective oxide layer along any surface that comes into contact with the launch vehicle to prevent them from being cold welded into place by extreme stress.
Components:
CubeSats often carry multiple on-board computers for the sake of carrying out research, as well providing for attitude control, thrusters, and communications. Typically, other on-board computers are included to ensure that the main computer is not overburdened by multiple data streams, but all other on-board computers must be capable of interfacing with it.
An example of a 3U cubesat – 3 1U cubes stacked. This cubesat size could function as the telescope of a two cubesat telescope system. It could be a simple 10 cm diameter optic system or use fancier folding optics to improve its resolving power. Credit: LLNL
Typically, a primary computer is responsible for delegating tasks to other computers – such as attitude control, calculations for orbital maneuvers, and scheduling tasks. Still, the primary computer may be used for payload-related tasks, like image processing, data analysis, and data compression.
Miniaturized components provide attitude control, usually consisting of reaction wheels, magnetorquers, thrusters, star trackers, Sun and Earth sensors, angular rate sensors, and GPS receivers and antennas. Many of these systems are often used in combination in order to compensate for shortcomings, and to provide levels of redundancy.
Sun and star sensors are used to provide directional pointing, while sensing the Earth and its horizon is essential for conducting Earth and atmospheric studies. Sun sensors are also useful in ensuring that the CubsSat is able to maximize its access to solar energy, which is the primary means of powering a CubeSat – where solar panels are incorporated into the satellites outer casing.
Meanwhile, propulsion can come in a number of forms, all of which involve miniaturized thrusters providing small amounts of specific impulse. Satellites are also subject to radiative heating from the Sun, Earth, and reflected sunlight, not to mention the heat generated by their components.
Will cubesats develop a new technological branch of astronomy? Goddard engineers are taking the necessary steps to make cubesat sized telescopes a reality. (Credit: NASA, UniverseToday/TRR)
As such, CubeSat’s also come with insulation layers and heaters to ensure that their components do not exceed their temperature ranges, and that excess heat can be dissipated. Temperature sensors are often included to monitor for dangerous temperature increases or drops.
For communications, CubeSat’s can rely on antennae that work in the VHF, UHF, or L-, S-, C- and X-bands. These are mostly limited to 2W of power due to the CubeSat’s small size and limited capacity. They can be helical, dipole, or monodirection monopole antennas, though more sophisticated models are being developed.
Propulsion:
CubeSats rely on many different methods of propulsion, which has in turn led to advancements in many technologies. The most common methods includes cold gas, chemical, electrical propulsion, and solar sails. A cold gas thruster relies on inert gas (like nitrogen) which is stored in a tank and released through a nozzle to generate thrust.
As propulsion methods go, it is the simplest and most useful system a CubeSat can use. It is also one of the safest too, since most cold gases are neither volatile nor corrosive. However, they have limited performance and cannot achieve high impulse maneuvers. Hence why they are generally used in attitude control systems, and not as main thrusters.
Miniaturized ion engines are a method of choice for providing thrust control for CubeSats. Credits: NASA
Chemical propulsion systems rely on chemical reactions to produce high-pressure, high-temperature gas which is then directed through a nozzle to create thrust. They can be liquid, solid, or a hybrid, and usually come down to the combination of chemicals combined with a catalysts or an oxidizer. These thrusters are simple (and can therefore be miniaturized easily), have low power requirements, and are very reliable.
Electric propulsion relies on electrical energy to accelerate charged particles to high speeds – aka. Hall-effect thrusters, ion thrusters, pulsed plasma thrusters, etc. This method is beneficial since it combines high specific-impulse with high-efficiency, and the components can be easily miniaturized. A disadvantage is that they require additional power, which means either larger solar cells, larger batteries, and more complex power systems.
Solar sails are also used as a method for propulsion, which is beneficial because it requires no propellant. Solar sails can also be scaled to the CubSat’s own dimensions, and the satellite’s small mass results in the greater acceleration for a given solar sail’s area.
However, solar sails still need to be quite large compared to the satellite, which makes mechanical complexity an added source of potential failure. At this time, few CubeSats have employed a solar sail, but it remains an area of potential development since it is the only method that needs no propellant or involves hazardous materials.
The Planetary Society’s LightSail-1 is one of the few concepts where a CubeSat relied on a solar sail. Credit: Josh Spradling/The Planetary Society.
Because the thrusters are miniaturized, they create several technical challenges and limitations. For instance, thrust vectoring (i.e. gimbals) is impossible with smaller thrusters. As such, vectoring must instead be achieved by using multiple nozzles to thrust asymmetrically or using actuated components to change the center of mass relative to the CubeSat’s geometry.
History:
Beginning in 1999, California Polytechnic State University and Stanford University developed the CubeSat specifications to help universities worldwide to perform space science and exploration. The term “CubeSat” was coined to denote nano-satellites that adhere to the standards described in the CubeSat design specifications.
These were laid out by aerospace engineering professor Jordi Puig-Suari and Bob Twiggs, from the Department of Aeronautics & Astronautics at Stanford University. It has since grown to become an international partnership of over 40 institutes that are developing nano-satellites containing scientific payloads.
Initially, despite their small size, academic institutions were limited in that they were forced to wait, sometimes years, for a launch opportunity. This was remedied to an extent by the development of the Poly-PicoSatellite Orbital Deployer (otherwise known as the P-POD), by California Polytechnic. P-PODs are mounted to a launch vehicle and carry CubeSats into orbit and deploy them once the proper signal is received from the launch vehicle.
The BisonSat is one example of a CubeSat mission launched by NASA’s CubeSat Launch Initiative on Oct. 8, 2015. Credits: Salish Kootenai College
The purpose of this, according to JordiPuig-Suari, was “to reduce the satellite development time to the time frame of a college student’s career and leverage launch opportunities with a large number of satellites.” In short, P-PODs ensure that many CubeSats can be launched at any given time.
Several companies have built CubeSats, including large-satellite-maker Boeing. However, the majority of development comes from academia, with a mixed record of successfully orbited CubeSats and failed missions. Since their inception, CubeSats have been used for countless applications.
For example, they have been used to deploy Automatic Identification Systems (AIS) to monitor marine vessels, deploy Earth remote sensors, to test the long term viability of space tethers, as well as conducting biological and radiological experiments.
Within the academic and scientific community, these results are shared and resources are made available by communicating directly with other developers and attending CubeSat workshops. In addition, the CubeSat program benefits private firms and governments by providing a low-cost way of flying payloads in space.
An artist’s rendering of MarCO A and B during the descent of InSight. NASA/JPL-Caltech
In 2010, NASA created the “CubeSat Launch Initiative“, which aims to provide launch services for educational institutions and non-profit organizations so they can get their CubeSats into space. In 2015, NASA initiated its Cube Quest Challenge as part of their Centennial Challenges Programs.
With a prize purse of $5 million, this incentive-competition aimed to foster the creation of small satellites capable of operating beyond low Earth orbit – specifically in lunar orbit or deep space. At the end of the competition, up to three teams will be selected to launch their CubeSat design aboard the SLS-EM1 mission in 2018.
NASA’s InSight lander mission (scheduled to launch in 2018), will also include two CubeSats. These will conduct a flyby of Mars and provide additional relay communications to Earth during the lander’s entry and landing.
Designated Mars Cube One (MarCO), this experimental 6U-sized CubeSat will will be the first deep-space mission to rely on CubeSat technology. It will use a high-gain, flat-paneled X-band antenna to transmit data to NASA’s Mars Reconnaissance Orbiter (MRO) – which will then relay it to Earth.
NASA engineers Joel Steinkraus and Farah Alibay demonstrate a full-scale mechanical mock-up of a MarCo CubeSat. Credit: NASA/JPL-Caltech
Making space systems smaller and more affordable is one of the hallmarks of the era of renewed space exploration. It’s also one of the main reasons the NewSpace industry has been growing by leaps and bounds in recent years. And with greater levels of participation, we are seeing greater returns when it comes to research, development and exploration.
