7. May 2018
As InSight begins its journey [Mars] to Mars, communications between the Red Planet and Earth over the next decade could represent a potential gap in data relay capability. With its current fleet of orbiter spaceships under development with no new NASA orbiter, SpaceFlight Insider explored the options available to maintain data relay capabilities with spacecraft on the surface in the 2020s.
Communication with spacecraft Surface of Mars is not an easy task. A number of limiting factors, including the rotation of the planet, the number of spacecraft on Mars and the weak signals transmitted by surface spacecraft, can make consistent and rapid direct communication from the surface of Mars to Earth a challenge , To enable a more consistent and reliable flow of data between spacecraft and their operators on Earth, since the early 2000s, a data relay using a Mars orbiting spacecraft has been consistently deployed.
The venerable Mars Global Surveyor (MGS) and Mars Odyssey (Odyssey) spacecraft were the first to use data relay capabilities in the modern era of Mars exploration. They served as relays for the twin missions of the Mars Exploration Rover (MER) until the arrival of the Mars Reconnaissance Orbiter (MRO) in 2006. MGS entered a safe mode in November 2006 and NASA declared the mission failed later in January 2007 to restore contact with the aging orbiter. The 12-year-old MRO and the 17-year-old Odyssey have since served as primary data relays for Mars surface missions.
The value of using spacecraft as relays has proved invaluable. From a technical point of view, it enables a reduction of the overall spacecraft mass for lander by reducing the equipment requirements for communication payloads. For mission operators, it allows them to plan more intensive schedules for lander and rover by reducing the time it takes to send and receive data, a task that is accomplished by limited transmissions during the orbit of spacecraft in windows. Project scientists and researchers also see a benefit in the fact that the volume of science that can be returned from the surface, thanks to the shortening of time for communication with the earth and the increase in scientific activities
Where is the Replacement?  By the end of 2016, proposals to fund options for the development of a replacement communications and science orbiter to be sent to Mars during the 2022 launch were funded. The mission proposals for the Mars 2022 Orbiter (also called the Next Mars Orbiter or NeMO) were different, but focused on several common elements. Primary design elements for NeMO include solar electric ion drive and the use of broadband optical (laser) communication .
The ion propulsion could serve as a demonstration of technology in a Mars exploration environment, as well as the ability to serve as a recirculation vehicle for the transport of samples during the planned Mars sample recirculation mission. In addition, instrumentation for NeMO would build on MRO's legacy hardware and ensure continuity in the high-resolution imaging and remote sensing observations collected on Mars over the last two decades. However, funding for NeMO has been largely phased in favor of limited funding for the development of the Mars Sample Return mission. The primary goal of Mars Sample Return is to collect samples that scientists want to collect and cache with the Mars 2020 Rover currently under development. Planetary Science's recent Decadal Survey has listed the flagship sample recirculation mission as the primary target for NASA's Mars program in the 2020s along with the required funding. While the existing fleet of Mars in orbit is healthy, it does mean that moving a new orbiter will require careful management of existing orbitals over the next decade.
When asked about NASA plans to rely on current spacecraft Richard Zurek, MRO project scientist, remains confident that relay capabilities will continue until the 2020s. Dr. Zurek is also a member of NASA's Mars Exploration Program Research Group (MEPAG) and currently Chief Scientist of the Mars Program Office at the Jet Propulsion Laboratory (JPL).
"There are concerns that the assets we have are aging, but the program is looking for options to fill the gap," Dr. Zurek on the valuation of existing orbital investments by MEPAG. "Hopefully, future resources will include MRO, we do not count on Odyssey [over the long term] but we also want to put MAVEN in a more appropriate orbit in the future."
Options Are Moving Forward
From the perspective of age alone, Mars Odyssey has far surpassed the lifespan of its main mission, which ended in August 2004. Despite the occasional entry into a protective mode the failure of one of its three main flywheels in 2012 may date as its biggest equipment malfunction. The failure of the flywheel required the commissioning of a fourth spare wheel, and the spacecraft has since worked nominally. Scientists have previously stated that Odyssey, if there is no major equipment failure, has enough fuel for further operation by 2025.
Assuming that Odyssey stops operating in front of other spacecraft, the MRO must handle data relays for current and planned missions to advance to the surface. According to Dr. Zurek has enough fuel for the MRO to do so until at least 2027. However, additional spacecraft may be operational on Mars to provide additional support and redundancy.
While Orbital Tilts Are Not Ideal If you support the current data relay workload, the ExoMars Trace Gas Orbiter and Mars Atmospheric and Volatile Evolution (MAVEN) mission can provide limited support when needed. Both spacecraft carry Electra UHF transmitters similar to those on MRO so they can communicate with spacecraft on the surface. An early test of MAVENS Relay Capabilities in 2014 showed its effectiveness in data relays with a transmission of 550 gigabits – or more than half a terabyte – of information from Curiosity during a single run ,
It is planned to adjust ExoMars and MAVEN's orbits as soon as their primary goals for the scientific mission are achieved in the years to come, in order to be better able to assist in data forwarding in the future. They do not carry enough fuel to suit their inclinations, and so the consistency of their relay services would not be as common as Odyssey or MRO.
New techniques are being developed to help with data relays in the future. The InSight mission will, for the first time, test the deployment and operational capability of cubeSats on Mars to relay information during mission entry, descent and landing (EDL). Data routed during the EDL provides critical technical data on the condition of the spacecraft and may be useful for engineers to diagnose sources of error if the landing attempt fails. However, their use is limited for extended data transmission, in part due to the energy requirements and their inability to carry fuel and navigation equipment required to host the spacecraft.
"Cubesats are ideal for short bursts, but not ideal for larger data sets or data rates," Dr. Zurek. "Other communication systems also talk about optical communication, which is possible for increasing data rates on the road."
With regard to the management of existing facilities, the MRO team already uses Strategies to manage the MRO navigation equipment, energy resources and fuel reserves in the future. In March, the mission operators steered the spacecraft to an all-stellar navigation method to preserve the integrated inertia measurement units (IMUs) only for larger spacecraft adjustments. The all-stellar method uses on-board cameras to track stars as reference points to ensure that the spacecraft is aimed at Mars and can be used indefinitely without any of the cameras failing.
The Mission Team works to conserve MRO energy resources The batteries are prepared to take on more charge by gradually adjusting the spacecraft's orbit so that they spend less time in the shadow of the planet. When asked about the performance requirements for data relays and the ability to continue at the current rate of scientific observations, Dr. Zurek points out that MRO does not need much power for relay capabilities.
"There should be enough energy from the sun panels to support the data relays and scientific capabilities," Zurek said. "The problem is first and foremost to make sure the spacecraft does not consume low voltage and keep the batteries in good condition."
The rational steering of power and navigation resources makes fuel the most important limiting factor. Just under 200 kg (440 lbs) of fuel remain aboard for course corrections and other orbital adjustments that Dr. Ing. Zurek estimates that they can get the vehicle until at least 2027.
All options considered, MRO will likely remain the workhorse data relays that go into the 2020s, and a task that Dr. Ing. Zurek and the MRO team welcome. In the meantime, the development of a new orbiter will remain on NASA's wish list for future budget inquiries. If no new money is allocated to the project, a new telecommunications orbiter can not be sent to Mars until the second half of the 2020s.
Paul is currently a student in Space and Planetary Sciences at the University of Akransas in Fayetteville. Growing up in the Kansas City area, he developed an interest in space early in the Twin Mars Exploration Rover missions at an early age. He began his aerospace engineering studies before moving to Earth Sciences at Wichita State University. After working as an environmental geologist for a civil engineering office, he began his PhD in 2016 and is actively working on a doctoral thesis focusing on the surface processes of Mars , In 2014, he participated in a two-week simulation at the Mars Desert Research Station of the Mars Society and is still involved in analog mission studies today. Www.mjfriendship.de/de/index.php?op…80&Itemid=58 During the past years, Paul has been interested in scientific contacts and communication, which in the past has been a personal blog on space research from high school to university. Englisch: www.mjfriendship.de/en/index.php?op…31&Itemid=32 included. In recent years, he gave lectures on geology and environment space at schools and other organizations. He is pleased to contribute his experience as a geologist and scientist to the Spaceflight Insider team, which mainly writes on space research topics.