Capabilities of Gossamer-1 derived small spacecraft solar sails carrying MASCOT-derived nanolanders for in-situ surveying of NEAs

Any effort which intends to physically interact with specific asteroids requires understanding at least of the composition and multi-scale structure of the surface layers, sometimes also of the interior. Therefore, it is necessary first to characterize each target object sufficiently by a precursor mission to design the mission which then interacts with the object. In small solar system body (SSSB) science missions, this trend towards landing and sample-return missions is most apparent. It also has led to much interest in MASCOT-like landing modules and instrument carriers. They integrate at the instrument level to their mothership and by their size are compatible even with small interplanetary missions. The DLR-ESTEC Gossamer Roadmap NEA Science Working Groups‘ studies identified Multiple NEA Rendezvous (MNR) as one of the space science missions only feasible with solar sail propulsion. Parallel studies of Solar Polar Orbiter (SPO) and Displaced L1 (DL1) space weather early warning missions studies outlined very lightweight sailcraft and the use of separable payload modules for operations close to Earth as well as the ability to access any inclination and a wide range of heliocentric distances. These and many other studies outline the unique capability of solar sails to provide access to all SSSB, at least within the orbit of Jupiter. Since the original MNR study, significant progress has been made to explore the performance envelope of near-term solar sails for multiple NEA rendezvous. However, although it is comparatively easy for solar sails to reach and rendezvous with objects in any inclination and in the complete range of semi-major axis and eccentricity relevant to NEOs and PHOs, it remains notoriously difficult for sailcraft to interact physically with a SSSB target object as e.g. the Hayabusa missions do. The German Aerospace Center, DLR, recently brought the Gossamer solar sail deployment technology to qualification status in the Gossamer-1 project. Development of closely related technologies is continued for very large deployable membrane-based photovoltaic arrays in the GoSolAr project. We expand the philosophy of the Gossamer solar sail concept of efficient multiple sub-spacecraft integration to also include landers for one-way in-situ investigations and sample-return missions. These are equally useful for planetary defence scenarios, SSSB science and NEO utilization. We outline the technological concept used to complete such missions and the synergetic integration and operation of sail and lander. We similarly extend the philosophy of MASCOT and use its characteristic features as well as the concept of Constraints-Driven Engineering for a wider range of operations

Small Spacecraft Based Multiple Near-Earth Asteroid Rendezvous and Landing with Near-Term Solar Sails and ‘Now-Term‘ Technologies

Physical interaction with small solar system bodies (SSSB) is the next step in planetary science, planetary in-situ resource utilization (ISRU), and planetary defense (PD). It requires a broader understanding of the surface properties of the target objects, with particular interest focused on those near Earth. Knowledge of composition, multi-scale surface structure, thermal response, and interior structure is required to design, validate and operate missions addressing these three fields. The current level of understanding is occasionally simplified into the phrase, ”If you’ve seen one asteroid, you’ve seen one asteroid”, meaning that the in-situ characterization of SSSBs has yet to cross the threshold towards a robust and stable scheme of classification. This would enable generic features in spacecraft design, particularly for ISRU and science missions. Currently, it is necessary to characterize any potential target object sufficiently by a dedicated pre-cursor mission to design the mission which then interacts with the object in a complex fashion. To open up strategic approaches, much broader in-depth characterization of potential target objects would be highly desirable. In SSSB science missions, MASCOT-like nano-landers and instrument carriers which integrate at the instrument level to their mothership have met interest. By its size, MASCOT is compatible with small interplanetary missions. The DLR-ESTEC Gossamer Roadmap Science Working Groups‘ studies identified Multiple Near-Earth asteroid (NEA) Rendezvous (MNR) as one of the space science missions only feasible with solar sail propulsion. The Solar Polar Orbiter (SPO) study showed the ability to access any inclination, theDisplaced-L1 (DL1) mission operates close to Earth, where objects of interest to PD and for ISRU reside. Other studies outline the unique capability of solar sails to provide access to all SSSB, at least within the orbit of Jupiter, and significant progress has been made to explore the performance envelope of near-term solar sails for MNR. However, it is difficult for sailcraft to interact physically with a SSSB. We expand and extend the philosophy of the recently qualified DLR Gossamer solar sail deployment technology using efficient multiple sub-spacecraft integration to also include landers for one-way in-situ investigations and sample-return missions by synergetic integration and operation of sail and lander. The MASCOT design concept and its characteristic features have created an ideal counterpart for thisand has already been adapted to the needs of the AIM spacecraft, former part of the NASA-ESA AIDA mission. Designing the combined spacecraft for piggy-back launch accommodation enables low-cost massively parallel access to the NEA population

Solar Sails for Planetary Defense and High-Energy Missions

20 years after the successful ground deployment test of a (20 m)² solar sail at DLR Cologne, and in the light of the upcoming U.S. NEAscout mission, we provide an overview of the progress made since in our mission and hardware design studies as well as the hardware built in the course of our solar sail technology development. We outline the most likely and most efficient routes to develop solar sails for useful missions in science and applications, based on our developed ‘now-term’ and near-term hardware as well as the many practical and managerial lessons learned from the DLR-ESTEC GOSSAMER Roadmap. Mission types directly applicable to planetary defense include single and Multiple NEA Rendezvous ((M)NR) for precursor, monitoring and follow-up scenarios as well as sail-propelled head-on retrograde kinetic impactors (RKI) for mitigation. Other mission types such as the Displaced L1 (DL1) space weather advance warning and monitoring or Solar Polar Orbiter (SPO) types demonstrate the capability of near-term solar sails to achieve asteroid rendezvous in any kind of orbit, from Earth-coorbital to extremely inclined and even retrograde orbits. Some of these mission types such as SPO, (M)NR and RKI include separable payloads. For one-way access to the asteroid surface, nanolanders like MASCOT are an ideal match for solar sails in micro-spacecraft format, i.e. in launch configurations compatible with ESPA and ASAP secondary payload platforms. Larger landers similar to the JAXA-DLR study of a Jupiter Trojan asteroid lander for the OKEANOS mission can shuttle from the sail to the asteroids visited and enable multiple NEA sample-return missions. The high impact velocities and re-try capability achieved by the RKI mission type on a final orbit identical to the target asteroid‘s but retrograde to its motion enables small spacecraft size impactors to carry sufficient kinetic energy for deflection

Small Spacecraft Based Multiple Near-Earth Asteroid Rendezvous and Landing with Near-Term Solar Sails and ‘Now-Term‘ Technologies

Physical interaction with small solar system bodies (SSSB) is the next step in planetary science, planetary in-situ resource utilization (ISRU), and planetary defense (PD). It requires a broader understanding of the surface properties of the target objects, with particular interest focused on those near Earth. Knowledge of composition, multi-scale surface structure, thermal response, and interior structure is required to design, validate and operate missions addressing these three fields. The current level of understanding is occasionally simplified into the phrase, ”If you’ve seen one asteroid, you’ve seen one asteroid”, meaning that the in-situ characterization of SSSBs has yet to cross the threshold towards a robust and stable scheme of classification. This would enable generic features in spacecraft design, particularly for ISRU and science missions. Currently, it is necessary to characterize any potential target object sufficiently by a dedicated pre-cursor mission to design the mission which then interacts with the object in a complex fashion. To open up strategic approaches, much broader in-depth characterization of potential target objects would be highly desirable. In SSSB science missions, MASCOT-like nano-landers and instrument carriers which integrate at the instrument level to their mothership have met interest. By its size, MASCOT is compatible with small interplanetary missions. The DLR-ESTEC Gossamer Roadmap Science Working Groups‘ studies identified Multiple Near-Earth asteroid (NEA) Rendezvous (MNR) as one of the space science missions only feasible with solar sail propulsion. The Solar Polar Orbiter (SPO) study showed the ability to access any inclination, theDisplaced-L1 (DL1) mission operates close to Earth, where objects of interest to PD and for ISRU reside. Other studies outline the unique capability of solar sails to provide access to all SSSB, at least within the orbit of Jupiter, and significant progress has been made to explore the performance envelope of near-term solar sails for MNR. However, it is difficult for sailcraft to interact physically with a SSSB. We expand and extend the philosophy of the recently qualified DLR Gossamer solar sail deployment technology using efficient multiple sub-spacecraft integration to also include landers for one-way in-situ investigations and sample-return missions by synergetic integration and operation of sail and lander. The MASCOT design concept and its characteristic features have created an ideal counterpart for thisand has already been adapted to the needs of the AIM spacecraft, former part of the NASA-ESA AIDA mission. Designing the combined spacecraft for piggy-back launch accommodation enables low-cost massively parallel access to the NEA population

Flights Are Ten a Sail – Re-use and Commonality in the Design and System Engineering of Small Spacecraft Solar Sail Missions with Modular Hardware for Responsive and Adaptive Exploration

The exploration of small solar system bodies started with fast fly-bys of opportunity on the sidelines of missions to the planets. The tiny new worlds seen turned out to be so intriguing and different from all else(and each other) that dedicated sample-return and in-situ analysis missions were developed and launched. Through these, highly efficient low-thrust propulsion expanded from commercial use into mainstream and flagship science missions, there in combination with gravity assists. In parallel, the growth of small spacecraft solutions accelerated in numbers as well as individual spacecraft capabilities. The on-going missions OSIRIS-REx (NASA) or Hayabusa2 (JAXA) with its landers MINERVA-II and MASCOT, and the upcoming NEA scout mission are examples of this synergy of trends. The continuation of these and other related developments towards a propellant-less and highly efficient class of spacecraft for solar system exploration emerges in the form of small spacecraft solar sails designed for carefree handling and equipped with carried landers and application modules. These address the needs of all asteroid user communities– planetary science, planetary defence, and in-situ resource utilization – as well as other fields of solar system science and applications such as space weather warning and solar observations. Already the DLR-ESTEC GOSSAMER Roadmap for Solar Sailing initiated studies of missions uniquely feasible with solar sails such as Displaced L1 (DL1) space weather advance warning and monitoring and Solar Polar Orbiter(SPO) delivery, which demonstrate the capabilities of near-term solar sails to reach any kind of orbit in the inner solar system. This enables Multiple Near-Earth Asteroid (NEA) rendezvous missions (MNR),from Earth-coorbital to extremely inclined and even retrograde target orbits. For these mission types using separable payloads, design concepts can be derived from the separable Boom Sail Deployment Units characteristic of DLR GOSSAMER solar sail technology, nanolanders like MASCOT, or microlanders like the JAXA-DLR Jupiter Trojan Asteroid Lander for the OKEANOS mission which can shuttle from the sail to the targets visited and enable multiple NEA sample-return missions. These nanospacecraft scale components are an ideal match creating solar sails in micro-spacecraft format whose launch configurations are compatible with secondary payload platforms such as ESPA and ASAP. The DLR GOSSAMER solar sail technology builds on the experience gained in the development of deployable membrane structures leading up to the successful ground deployment test of a (20 m) solar sail at DLR Cologne in 1999 and in the 20 years since

From Sail to Soil - Getting Sailcraft out of the Harbour on a Visit to One of Earth's Nearest Neighbours

The DLR-ESTEC GOSSAMER roadmap envisages the development of solar sailing by successive low-cost technology demonstrators towards first science missions. In this framework, the GOSSAMER-1 deployment demonstrator for a (5 m)² sail structure in low Earth orbit is followed by a (20 m)² sail effect demonstrator GOSSAMER-2 for higher Earth orbits, and the (50 m)² GOSSAMER-3 sailcraft to prove the principle within the Earth-Moon system. Missions requiring the unique capabilities of solar sail propulsion were studied by science working groups, including multiple NEO rendezvous and fly-by. The GOSSAMER sail technology has been developed by DLR since the 1990s, with a successful (20 m)² deployment test in 1999 at DLR Cologne. The requirements for GOSSAMER-3 demand the demonstration of sufficient trajectory and attitude control for science missions. Advances in boom, sail, and deployment mechanisms have already now increased the payload margin of baseline GOSSAMER-3 designs from a few to several kg. A camera to demonstrate attitude control and a magnetometer to study the space environment around a sail were first considered as payloads for GOSSAMER-3. In addition to these, the shoebox-sized 10 kg asteroid lander MASCOT recently launched with HAYABUSA-2 also carries a hyperspectral infrared soil microscope and a surface thermal infrared radiometer. The camera‘s and radiometer‘s fields of view coincide on the asteroid surface. Although designed for a mission on (162173) 1999 JU3, with the necessary margins for the unknown the instruments are versatile enough to adapt. Thus, a minimal modification of MASCOT may be integrated as separable instrument module with GOSSAMER-3, first to observe the sail during the deployment and demonstration flight phases. In an extended mission and with experience previously gained, the mission could be concluded by the rendezvous with and the challenging drop of a ballistic lander onto a small asteroid near Earth. For the exercise scenario on the mitigation of fictional Earth impactor 2015 PDC, it is assumed that the GOSSAMER roadmap keeps its 2 year mission interval after the last expected launch date for GOSSAMER-1; the HAYABUSA-2 mission proceeds successfully; the MASCOT Flight Spare become Ground Reference Model is preserved flightworthy and released from duty ½ year after the landing of MASCOT on 1999 JU3 to be mated to a likely GOSSAMER-3 design prepared for but not depending on this opportunity. The combined spacecraft may: fly a technology demonstration mission extended to end at a nearby NEA; proceed directly to 2015 PDC for a fast flyby, a rendezvous and lander drop, or both; or abort the already begun tech-demo mission and midways change course towards the newly recognized threat

Paths not taken – the GOSSAMER roadmap’s other options

Highly efficient low-thrust propulsion is increasingly applied beyond commercial use, also in mainstream and flagship science missions, in combination with gravity assist propulsion. Another recent development is the growth of small spacecraft solutions, not in size but in numbers and individual capabilities. Just over ten years ago, the DLR-ESTEC GOSSAMER Roadmap to Solar Sailing was set up to guide technology developments towards a propellant-less and highly efficient class of spacecraft for solar system exploration and applications missions: small spacecraft solar sails designed for carefree handling and equipped with carried application modules. Soon, in three dedicated GOSSAMER Roadmap Science Working Groups it initiated studies of missions uniquely feasible with solar sails such as Displaced L1 (DL1) space weather advance warning and monitoring, Solar Polar Orbiter (SPO) delivery to very high inclination heliocentric orbit, and multiple Near-Earth Asteroid (NEA) rendezvous (MNR). Together, they demonstrate the capability of near-term solar sails to achieve at least in the inner solar system almost any kind of heliocentric orbit within 10 years, from the Earth-co-orbital to the extremely inclined, eccentric and even retrograde. Noted as part of the MNR study, sail-propelled head-on retrograde kinetic impactors (RKI) go to this extreme to achieve the highest possible specific kinetic energy for the deflection of hazardous asteroids. At DLR, the experience gained in the development of deployable membrane structures leading up to the successful ground deployment test of a (20 m)², i.e., 20 m by 20 m square solar sail at DLR Cologne in 1999 was revitalized and directed towards a 3-step small spacecraft development line from as-soon-as-possible sail deployment demonstration (GOSSAMER-1) via in-flight evaluation of sail attitude control actuators (GOSSAMER-2) to an envisaged proving-the-principle flight in the Earth-Moon system (GOSSAMER-3). First, it turned the concept of solar sail deployment on its head by introducing four separable Boom Sail Deployment Units (BSDU) to be discarded after deployment, enabling lightweight 3-axis stabilized sailcraft. By 2015, this effort culminated in the ground-qualified technology of the DLR GOSSAMER-1 deployment demonstrator Engineering Qualification Model (EQM). For mission types using separable payloads, such as SPO, MNR and RKI, design concepts can be derived from the BSDU characteristic of DLR GOSSAMER solar sail technology which share elements with the separation systems of asteroid nanolanders like MASCOT. These nano-spacecraft are an ideal match for solar sails in micro-spacecraft format whose launch configurations are compatible with ESPA and ASAP secondary payload platforms. Like any roadmap, this one contained much more than the planned route from departure to destination and the much shorter distance actually travelled. It is full of lanes, narrow and wide, detours and shortcuts, options and decision branches. Some became the path taken on which we previously reported. More were explored along the originally planned path or as new sidings in search of better options when circumstance changed and the project had to take another turn. But none were dead ends, they just faced the inevitable changes when roadmaps face realities and they were no longer part of the road ahead. To us, they were valuable lessons learned or options up our sleeves. But for future sailors they may be on their road ahead

Small Spacecraft Solar Sailing for Small Solar System Body Multiple Rendezvous and Landing

Physical interaction with small solar system bodies (SSSB) is the next step in planetary science, planetary in-situ resource utilization (ISRU), and planetary defense (PD). It requires a broader understanding of the surface properties of the target objects, with particular interest focused on those near Earth. Knowledge of composition, multi-scale surface structure, thermal response, and interior structure is required to design, validate and operate missions addressing these three fields. The current level of understanding is occasionally simplified into the phrase, "If you've seen one asteroid, you've seen one Asteroid", meaning that the in-situ characterization of SSSBs has yet to cross the threshold towards a robust and stable scheme of classification. This would enable generic features in spacecraft design, particularly for ISRU and science missions. Currently, it is necessary to characterize any potential target object sufficiently by a dedicated pre-cursor mission to design the mission which then interacts with the object in a complex fashion. To open up strategic approaches, much broader in-depth characterization of potential target objects would be highly desirable. In SSSB science missions, MASCOT-like nano-landers and instrument carriers which integrate at the instrument level to their mothership have met interest. By its size, MASCOT is compatible with small interplanetary missions. The DLR-ESTEC Gossamer Roadmap Science Working Groups' studies identified Multiple Near-Earth asteroid (NEA) Rendezvous (MNR) as one of the space science missions only feasible with solar sail propulsion. The Solar Polar Orbiter (SPO) study showed the ability to access any inclination and a wide range of heliocentric distances, with a separable payload module delivered by sail to the proper orbit. The Displaced-L1 (DL1) spaceweather early warning mission study sailcraft operates close to Earth, where all objects of interest to PD must pass and low delta-v objects for ISRU reside. Other studies outline the unique capability of solar sails to provide access to all SSSB, at least within the orbit of Jupiter, and significant progress has been made to explore the performance envelope of near-term solar sails for MNR. However, it is difficult for sailcraft to interact physically with a SSSB. We expand and extend the philosophy of the recently qualified DLR Gossamer solar sail deployment technology using efficient multiple sub-spacecraft integration to also include landers for one-way in-situ investigations and sample-return missions by synergetic integration and operation of sail and lander. The MASCOT design concept and its characteristic features have created an ideal counterpart for this. For example, the MASCOT Mobility hopping mechanism and its power supply concept have already been adapted to the specific needs of MASCOT2 which was to be carried on the AIM spacecraft of ESA as part of the NASA-ESA AIDA mission to binary NEA Didymos. The methods used or developed in the realization of MASCOT such as Concurrent Engineering, Constraints-Driven Engineering and Concurrent Assembly Integration and Verification enable responsive missions based on now available as well as near-term technologies. Designing the combined spacecraft for piggy-back launch accommodation enables low-cost massively parallel access to the NEA population