Mars Express Forward Link Capabilities for the Mars Relay Operations Service (MaROS)
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This software provides a new capability for landed Mars assets to perform forward link relay through the Mars Express (MEX) European Union orbital spacecraft. It solves the problem of standardizing the relay interface between lander missions and MEX. The Mars Operations Relay Service (MaROS) is intended as a central point for relay planning and post-pass analysis for all Mars landed and orbital assets. Through the first two phases of implementation, MaROS supports relay coordination through the Odyssey orbiter and the Mars Reconnaissance Orbiter (MRO). With this new software, MaROS now fully integrates the Mars Express spacecraft into the relay picture. This new software generates and manages a new set of file formats that allows for relay request to MEX for forward and return link relay, including the parameters specific to MEX. Existing MEX relay planning interactions were performed via email exchanges and point-to-point file transfers. By integrating MEX into MaROS, all transactions are managed by a centralized service for tracking and analysis. Additionally, all lander missions have a single, shared interface with MEX and do not have to integrate on a mission-by mission basis. Relay is a critical element of Mars lander data management. Landed assets depend largely upon orbital relay for data delivery, which can be impacted by the availability and health of each orbiter in the network. At any time, an issue may occur to prevent relay. For this reason, it is imperative that all possible orbital assets be integrated into the overall relay picture.Keywords:
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Relay communication satellites play a very important role on the lunar far side and pole areas exploration missions. Queqiao relay communication satellite was developed to provide relay communication support for the lander and the rover of Chang’e-4 mission landing on the far side of the Moon. From entering into the halo mission orbit around Earth-Moon libration point 2 on June 14, 2018, it has operated on the orbit more than thirty months. It worked very well and provided reliable, continuous relay communication support for the lander and the rover to accomplish the goals of Chang’e-4 lunar far side soft landing and patrol exploration mission. Exploration of the lunar south polar regions is of high scientific interest. A new relay communication satellite for Chinese south pole exploration mission is also under study. The system design and on-orbit operation status of Queqiao relay communication satellite were summarized in this paper. The system concept of the relay communication satellite for lunar south pole exploration missions is proposed. Finally, the future development and prospect of the lunar relay communication satellite system are given.
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A very significant challenge in the planetary mission design and operations is communications with ground control teams during critical events and highly risky maneuvers. These include entry, descent, and landing (EDL) and orbit insertion, which should not be carried out in the blind. Although vast planetary distances and long round-trip light times disallow real-time intervention from controllers, acquiring the relevant event performance parameters in near real-time can be imperative for determining the corrective actions needed immediately following or, in the case of significant anomalies, aid in the diagnostic analysis. During several previous Mars missions landing events, and the Huygens probe landing on Titan, the communications strategy relied on proximity links to planetary orbiters, which then relayed the data to the Deep Space Network (DSN). In addition, attempts were successfully made in parallel to receive the signal carrier directly at Earth often using large radio telescopes when the wavelength was outside the DSN’s reception bands. This Direct-to-Earth (DTE) back-up method was only possible due to special techniques utilizing the DSN’s open-loop Radio Science Receivers. In every case, it was very challenging since the link budget of a landing vehicles were designed for proximity orbiter relays and not for distances across the solar system. A new method is introduced since not all future missions can rely on the presence of pre-existing orbiters at their planetary targets to relay their critical data ad, furthermore, most missions would not likely have the resources to implement a reliable DTE link at acceptable data rates, bypassing a need for a relay asset. With the advent CubeSat form-factor spacecraft, one or more, for added reliability, CubeSats can be launched with the primary mission, travel to the target, and be positioned to view the critical event, such as EDL, and carry out real-time relay of the data to the DSN at higher rates. CubeSats have flown in the Earth environment but never flown or been operated in deep space or planetary environment so careful design as well as flight experience are needed. The relay function requires the development of radio and antenna systems to meet challenging specifications. After initial technical demonstration of the concept and operational experience, the cost can decrease as systems become more standardized with increased reliability. This paper describes the invention of the “carry your own relay” concept and the formulation of the mission likely to be the first planetary CubeSat mission called Mars Cube One (MarCO). It also describes the operational concept of relay small spacecraft and their role reducing mission risk as well as overall mission cost.
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Deep space exploration
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This study examines the methodology for operating and communicating with NASA's Mars Science Laboratory (MSL) Curiosity Rover during the 2019 solar conjunction. For MSL, solar conjunction occurs when the viewing angle between the Sun and Mars from Earth's perspective falls below 3 degrees, which occurs roughly every two Earth years and lasts for about two weeks. This presents a challenge for engineers operating a vehicle on Mars because the degraded signal to noise ratio disrupts data flow between Earth and the spacecraft. As a result, operators designate a command moratorium in which no commands are sent to the rover and instead design long-term plans that are uplinked weeks in advance (rather than the nominal case of daily uplinks). Coordinating communications with the rover leading up to and following conjunction requires negotiations with several orbiters, another lander, and the Deep Space Network (DSN) - each with their own set of constraints. It is the Strategic Comm Planning Team's job to oversee this coordination, which acts as a baseline for the conjunction planning cadence. In the 2019 conjunction, MSL's Comm team faced additional complications such as the arrival of two new spacecraft at Mars - NASA's InSight (NSY) and the ESA-Roscosmos ExoMars Trace Gas Orbiter (TGO). The team also utilized a set of new, complex planning tools that were developed to handle the intricate incorporation of these new spacecraft into the Mars relay environment, but which had never before been used for conjunction communication planning. Although experience with previous conjunctions provides guidance, each conjunction period presents unique challenges and finding the optimal solution each time is one of the hardest challenges that the Comm team faces.
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The 25th of December 2003 will always be remembered as one of the special, even historic, days for the European Space Agency (ESA). When precisely at the predicted time the spacecraft Mars Express emerged from behind the planet Mars, after a 40 minute burn of its main engine, and the first signal was received by the ground station, it became clear that one of the most ambitious challenges undertaken by the European Space Agency so far was a tremendous success: The safe insertion of a spacecraft into Mars orbit. It was a challenge in many aspects: a new generation of science missions, known as flexi missions, built and launched in record time with a minimum cost; a double mission having an orbiter and a lander, where the lander is ejected to its targeted site with high precision only a few days prior to inserting the orbiter into a Mars bound orbit; the first European attempt to send a spacecraft into orbit around another planet; the first European attempt to land on another planet. Looking at the history of attempts to orbit or land on the planet Mars, this is not an easy task. Out of the 39 missions sent out to the red planet, only 16 were successful. Out of those 16 missions 4 were flybys and 7 were landers, which leaves only 5 successful Mars orbit insertions. This shows how difficult it is to navigate a spacecraft over a distance of up to 400.000.000 km to a target planet in a safe and efficient way. Not only the final act of orbit insertion is important, it is the achievement of a long process from manufacturing of the spacecraft, team building, preparation of the ground segment and operations procedures, simulations, launch of the spacecraft, precise navigation and overcoming any obstacles and problems until the planet is in view. This requires a multiteam effort from various parties involved. This paper will elaborate on the organization and efforts that had to be made to achieve the goal, coping with the specific challenges of the Mars Express Mission and show why the Mars orbit insertion phase was so critical and exciting from the perspective of the Mars Express Flight Control Team.
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As part of the National Aeronautics and Space Administration (NASA) mission, the lunar exploration team has identified the Moon's south pole as a target for a robotics mission due the possibility of existence of water in the craters. The role of lunar relay satellites is to provide coverage for areas that do not have a direct view of the Earth. The lunar relay satellites and the Earth ground network supporting them are key for the many robotic and manned missions. In this type of mission, though similar to the Mars relay system, the design of the ground network in support of the lunar relay system requires attention to ground network infrastructure, spectrum, and tracking requirements. This paper will address the evolution of exploration ground stations and ground options to support the early lunar relay satellite (LRS-1) for robotics mission and its relation to manned relay (LRS-2 and LRS-3).
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The main purpose of the Small Space-Based Geosynchronous Earth orbiting (GEO) satellite is to provide a space link to the user mission spacecraft for relaying data through ground networks to user Mission Control Centers. The Small Space Based Satellite (SSBS) will provide services comparable to those of a NASA Tracking Data Relay Satellite (TDRS) for the same type of links. The SSBS services will keep the user burden the same or lower than for TDRS and will support the same or higher data rates than those currently supported by TDRS. At present, TDRSS provides links and coverage below GEO; however, SSBS links and coverage capability to above GEO missions are being considered for the future, especially for Human Space Flight Missions (HSF). There is also a rising need for the capability to support high data rate links (exceeding 1 Gbps) for imaging applications. The communication payload on the SSBS will provide S/Ka-band single access links to the mission and a Ku-band link to the ground, with an optical communication payload as an option. To design the communication payload, various link budgets were analyzed and many possible operational scenarios examined. To reduce user burden, using a larger-sized antenna than is currently in use by TDRS was considered. Because of the SSBS design size, it was found that a SpaceX Falcon 9 rocket could deliver three SSBSs to GEO. This will greatly reduce the launch costs per satellite. Using electric propulsion was also evaluated versus using chemical propulsion; the power system size and time to orbit for various power systems were also considered. This paper will describe how the SSBS will meet future service requirements, concept of operations, and the design to meet NASA users' needs for below and above GEO missions. These users' needs not only address the observational mission requirements but also possible HSF missions to the year 2030. We will provide the trade-off analysis of the communication payload design in terms of the number of links looking above and below GEO; the detailed design of a GEO SSBS spacecraft bus and its accommodation of the communication payload, and a summary of the trade study that resulted in the selection of the Falcon 9 launch vehicle to deploy the SSBS and its impact on cost reductions per satellite. ======================================================================== Several initiatives have taken place within NASA1 and international space agencies2 to create a human exploration strategy for expanding human presence into the solar system; these initiatives have been driven by multiple factors to benefit Earth. Of the many elements in the strategy one stands out: to send robotic and human missions to destinations beyond Low Earth Orbit (LEO), including cis-lunar space, Near-Earth Asteroids (NEAs), the Moon, and Mars and its moons.3, 4 The time frame for human exploration to various destinations, based on the public information available,1,4 is shown in Figure 1. Advance planning is needed to define how future space communications services will be provided in the new budget environment to meet future space communications needs. The spacecraft for these missions can be dispersed anywhere from below LEO to beyond GEO, and to various destinations within the solar system. NASA's Space Communications and Navigation (SCaN) program office provides communication and tracking services to space missions during launch, in-orbit testing, and operation phases. Currently, SCaN's space networking relay satellites mainly provide services to users below GEO, at Near Earth Orbit (NEO), below LEO, and in deep space. The potential exists for using a space-based relay satellite, located in the vicinity of various solar system destinations, to provide communication space links to missions both below and above its orbit. Such relays can meet the needs of human exploration missions for maximum connectivity to Earth locations and for reduced latency. In the past, several studies assessed the ability of satellite-based relays working above GEO in conjunction with Earth ground stations. Many of these focused on the trade between space relay and direct-to-Earth station links5,6,7. Several others focused on top-level architecture based on relays at various destinations8,9,10,11,12. Much has changed in terms of microwave and optical technology since the publication of the referenced papers; Ka-band communication systems are being deployed, optical communication is being demonstrated, and spacecraft buses are becoming increasingly more functional and operational. A design concept study was undertaken to access the potential for deploying a Small Space-Based Satellite (SSBS) relay capable of serving missions between LEO and NEO. The needs of future human exploration missions were analyzed, and a notional relay-based architecture concept was generated as shown in Fig. 1. Relay satellites in Earth through cis-Lunar orbits are normally located in stable orbits requiring low fuel consumption. Relay satellites for Mars orbit are normally selected based on the mission requirement and projected fuel consumption. Relay satellites have extreme commonalities of functions between them, differing only in the redundancy and frequencies used; therefore, the relay satellite in GEO was selected for further analysis since it will be the first step in achieving a relay-based architecture for human exploration missions (see Fig.Figure 2). The mission design methodology developed by the Collaborative Modeling for Parametric Assessment of Space Systems (COMPASS) team13 was used to produce the satellite relay design and to perform various design trades. At the start of the activity, the team was provided with the detailed concept of the notional architecture and the system and communication payload drivers.
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On June 2 nd 2003 Mars Express was launched from Baikonur and placed into its interplanetary trajectory to the Red Planet. The orbiter successfully entered Martian orbit 6 months later on 25 th December. During each orbit, Mars Express spends some time turned towards the planet for instrument observations and some time turned towards Earth for communications with ground stations; it is therefore necessary to find a good compromise in time-sharing between scientific observation and data relay to ground, since concurrent observation and data return to Earth are impossible. To deal with this peculiarity of the Mars Express mission, Industry, Project and the ESOC flight control team have had to study a new engineering solution that implements on-board storage of a large amount of data and its periodic daily downlink to Earth. Data collected by the orbiter instruments are transmitted to Earth at a rate between 28 to 180 kbps. Very variable amounts of scientific data are produced by the scientific instruments on board. These are stored temporarily on the Solid State Mass Memory recording device, and then downlinked from the spacecraft to Earth. From the ground station they are sent, via a ground line, to the European Space Operations Centre (ESOC) in Darmstadt, Germany, and stored in a dedicated Mars Express science data archive from which they are available to the various Principal Investigator teams. This paper will describe the data journey through a very complex communication chain. Mars exploration poses significant new challenges: most particularly the return of such a large data volumes from high-resolution surface instruments over limited telemetry bitrates. In this paper, the problems encountered on Mars Express with regard to data return are analyzed, and the derived solutions are examined.
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The ground station usage on the Mars Express mission is based on the ESTRACK network (ESA Deep Space Stations New Norcia and Cebreros) and on the NASA Deep Space Network. The allocation and scheduling of the required ground stations is an iterative process running over several months starting with the MEX Spacecraft Operation Manager’s long term station time requests and ending with the delivery of the final schedule to the different ground stations. This paper will describe the processes involved in the Mars Express mission as far as ground stations handling is concerned. Some of these processes have recently been automated. The reasons of this automation and how it was implemented will also be presented.
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The authors will report on a small lunar relay satellite concept, capable of fitting in a Minotaur V launch vehicle, to provide communication and navigation (C&N) services to users on the moon. Ultimately, the C&N system will provide multiple fixed and mobile users, human and robotic, with service from launch to lunar landing and throughout occupation. In order to provide complete coverage for users on the moon, a constellation of relay satellites will ultimately be required. In the near term, however, the relays will focus on certain important locations, particularly the South Polar region, where water may be located and early landings may occur. These locations are only visible from Earth antennas for 14 days of each 28 day time period, requiring a relay satellite to fill the gaps. One alternative for this satellite is a small, less costly lunar relay capable of launching on the relatively inexpensive Minotaur class of launch vehicles, the Minotaur V in particular. In this paper, this spacecraft concept will be discussed, including the mission context, concept of operations, mission requirements, payload concept, ground system concept and spacecraft concept. *This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
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