In situ science on Phobos with the Raman spectrometer for MMX (RAX): preliminary design and feasibility of Raman meausrements

Mineralogy is the key to understanding the origin of Phobos and its position in the evolution of the Solar System. In situ Raman spectroscopy on Phobos is an important tool to achieve the scientifc objectives of the Martian Moons eXploration (MMX) mission, and maximize the scientifc merit of the sample return by characterizing the mineral composition and heterogeneity of the surface of Phobos. Conducting in situ Raman spectroscopy in the harsh environment of Phobos requires a very sensitive, compact, lightweight, and robust instrument that can be carried by the compact MMX rover. In this context, the Raman spectrometer for MMX (i.e., RAX) is currently under development via international collaboration between teams from Japan, Germany, and Spain. To demonstrate the capability of a compact Raman system such as RAX, we built an instrument that reproduces the optical performance of the fight model using commercial of-the-shelf parts. Using this performance model, we measured mineral samples relevant to Phobos and Mars, such as anhydrous silicates, carbonates, and hydrous minerals. Our measurements indicate that such minerals can be accurately identifed using a RAX-like Raman spectrometer. We demonstrated a spectral resolution of approximately 10 cm−1, high enough to resolve the strongest olivine Raman bands at ~820 and ~850 cm−1, with highly sensitive Raman peak measurements (e.g., signal-to-noise ratios up to 100). These results strongly suggest that the RAX instrument will be capable of determining the minerals expected on the surface of Phobos, adding valuable information to address the question of the moon’s origin, heterogeneity, and circum-Mars material transport

Pointing and spectral assignment design and control for MERTIS

The development of MERTIS, a miniaturized thermal infrared imaging spectrometer onboard of ESA's cornerstone mission BepiColombo to Mercury has been completed. Qualification of the design is followed by the calibration of the instrument showing up first results of the technology used. Based on subsequent viewing of different targets including on-board calibration sources the push-broom instrument will use a 2-dimensional bolometer detector to provide spatial and spectral information. Here repetition accuracy of pointing and spectral assignment is supported by the design of instrument components under the restriction of limited resources. Additionally a concept of verification after launch and cruise phase of the mission was developed. The article describes how this has been implemented and what the results under environment testing are

Qualification and Calibration of DLR’s optical BiROS Payload

Direct optical communication links might offer a solution for the increasing demand of transmission capacity in satellite missions. Although direct space-to-ground links suffer from limited availability due to cloud coverage, the achievable data rates can be higher by orders of magnitude compared to traditional RF communication systems. DLR’s Institute of Communications and Navigation is currently developing an experimental communication payload for DLR’s BiROS satellite. The laser terminal consists of a tracking sensor with an uplink channel and two kinds of laser sources: a directly modulated High-Power Laser Diode (HPLD) and an Erbium Doped Fiber Amplifier (EDFA). This paper will give an overview about the hardware of the laser terminal with a special focus on the calibration of the optical system and the space-qualification, including a radiation test especially for the optical components. Further, the data reception and storage on ground station site will be discussed

From Observational Geometry to Practical Satellite Design: AsteroidFinder/SSB

DLR has selected AsteroidFinder as the first payload to be flown on its SSB satellite platform, in the frame of the German national Compact Satellite Program. The scientific goal is to better observe and characterize Near-Earth Objects (NEO), particularly the Aten asteroids and the Inner Earth Objects orbiting completely Interior to Earth’s Orbit (IEO). Only ten mostly Aten-like IEOs have been found so far, of which two are Potentially Hazardous Asteroids (PHA). Ground-based observations of Atens and IEOs are severely constrained by the Earth’s body and its atmosphere. An Earth-orbiting survey telescope can in principle evade these constraints with ease, to become an efficient and cost-effective tool to facilitate the discovery and follow-up of these objects. It may however be constrained by other factors specific to its orbital environment. Analysis of the observational geometry and present technological capabilities has shown that stray light from the Sun and Earth is the most critical performance limiter. The thermal influences of both sunlight and earthlight become important if the capabilities of state-of-the-art detectors are to be fully exploited at low temperatures. Thus, the optical and thermal behaviour of the satellite as a system beyond the scientific instrument itself is strongly coupled, through the shape and layout of the satellite and the parameters of the satellite’s orbit, to the observational geometry of the target asteroids, the Earth, and the Sun. Objects within the Earth’s orbit are to be observed in a region of interest continuing sunward from that covered by ground-based surveys to 30° solar elongation. Their identification is accomplished through apparent motion and parallax, requiring repeated observations of the same field which the satellite has to provide at certain intervals. The strong coupling of optical and thermal influences forces system-level optimization of the geometrical layout of the satellite in accordance with survey pointing patterns. This affects the layout of the telescope and the components visible to its aperture, the positioning of several radiators for different temperature levels, the accommodation of antennae for communication, the placement of deployable baffles, sunshields, and solar panels, etc. AsteroidFinder will also test space-based detection of space debris and artificial satellites at different observational attitudes. All this has to be fitted to the limited envelope of a compact class satellite; within the common envelope and power rating of a small household fridge, and no moving parts but one-time deployables. As of December 2008, AsteroidFinder/SSB is in preparation for phase B. Its launch is planned for 2012, for a one-year baseline mission

DESIS - DLR Earth Sensing Imaging Spectrometer

Space-based hyperspectral instruments are used in many applications requiring identification of materials or helping to monitor the environment. Although there are lots of useful applications, the amount of space born data is limited. The DLR Earth Sensing Imaging Spectrometer (DESIS) is a new space-based hyperspectral instrument developed by DLR and operated under collaboration between the German Aerospace Center (DLR) and Teledyne Brown Engineering (TBE). The primary goal of DESIS is to measure and analyze quantitative diagnostic parameters describing key processes on the Earth sur-face. This goal can be reached with the instrument parameters of 235 spectral bands from 400 nm to 1000 nm and a GSD of 30 m. DESIS was installed on the International Space Station on the MUSES platform in August 2018 and is providing hyperspectral Earth Observation in the wavelength range from visible to near-infrared with high resolution and near global coverage. This contribution presents the de-sign of the compact instrument. With its interface constraints it would be also suitable for small satellite platforms

On-Ground Calibration of DESIS: DLR´s Earth Sensing Imaging Spectrometer for the International Space Station ISS

On-ground calibration approach and selected results for DESIS have been presented. The DLR Earth Sensing Imaging Spectrometer (DESIS) as a new space-based hyperspectral instrument has built and finally calibrated by DLR and is ready for launch to International Space Station (ISS)

Small satellites for big science: the challenges of high-density design in the DLR Kompaktsatellit AsteroidFinder/SSB

The design of small satellites requires a paradigm shift in the thinking of satellite designers as well as mission scientists, payload users, and programme management - in brief, everyone involved. In a conventional approach, spacecraft design evolves in a mostly linear fashion from mission requirements by well-defined procedures through a series of reviews into a design space that is essentially not limited by constraints other than programmatic. The mission defines a pallet of instruments, their needs then shape the spacecraft bus, and the integrated spacecraft is finally mated to a dedicated launch, to be placed into an orbit carefully custom-tailored by mission analysis and continuously trimmed by on-board propulsion. Components are manufactured to spec, one-off plus spares, and painstaking testing has to iron out the many space firsts and compromises made in an arduous and protracted design process. Small satellite design reverses this comfortable line of thinking. It begins with hard, and not just programmatic constraints on most of the essential parameters that define a satellite. Launch as a secondary payload is the choice, not just for budgetary reasons, but due to the lack of viable dedicated launchers. It requires a small stowed envelope and a tightly limited mass budget. This results in limited surface area for solar panels and radiators. Small project volume enables a high flight cadence which makes re-use of designs and components desirable and feasible, in a self-catalyzing cycle. Re-use and constraints force the system perspective on every participant in a quick succession of sometimes diverging but generally converging iterations that lends itself to the Concurrent Engineering approach. There is simply no space left in a small satellite project for boxes to think in. To exploit the technological convergence that has created powerful and miniaturized science instruments and satellite components, the DLR research and development programme has initiated the Kompaktsatellit line of development. It is intended to enable dedicated missions for science projects that would earlier have resulted in one full-scale scientific instrument among many sharing a ride on a large platform without the perspective of follow-on within an academic career lifetime. In an internal competition, the AsteroidFinder instrument dedicated to the search for small bodies orbiting the Sun interior to Earth’s orbit has been selected as the payload to fly first on a Kompaktsatellit. Alongside, the Standard Satellite Bus kit, /SSB, is being developed, based on extensive re-use of experience, concepts, and components of the DLR satellites BIRD and TET. It is designed to avoid the overhead carried by pre-defined standard bus concepts while allowing for seamless integration of the payload into an organic spacecraft design. Challenges encountered and solutions found across the subsystems of AsteroidFinder/SSB will be presented

The Instrument Design of the DLR Earth Sensing Imaging Spectrometer (DESIS)

Whether for identification and characterization of materials or for monitoring of the environment, space-based hyperspectral instruments are very useful. Hyperspectral instruments measure several dozens up to hundreds of spectral bands. These data help to reconstruct the spectral properties like reflectance or emission of Earth surface or the absorption of the atmosphere, and to identify constituents on land, water, and in the atmosphere. There are a lot of possible applications, from vegetation and water quality up to greenhouse gas monitoring. But the actual number of hyperspectral space-based missions or hyperspectral space-based data is limited. This will be changed in the next years by different missions. The German Aerospace Center (DLR) Earth Sensing Imaging Spectrometer (DESIS) is one of the new currently existing space-based hyperspectral instruments, launched in 2018 and ready to reduce the gap of space-born hyperspectral data. The instrument is operating onboard the International Space Station, using the Multi-User System for Earth Sensing (MUSES) platform. The instrument has 235 spectral bands in the wavelength range from visible (400 nm) to near-infrared (1000 nm), which results in a 2.5 nm spectral sampling distance and a ground sampling distance of 30 m from 400 km orbit of the International Space Station. In this article, the design of the instrument will be described

Feasibility-Study OOS-RAV

With the objective of designing a mission to validate the DEOS robotic arm, a CE study named OOS-RAV (On Orbit Servicing– Robotic Arm Verification) was conducted. The defined mission was to approach a target satellite (either one already in orbit or a target satellite specifically designed and carried along with our spacecraft), and in close distances to grab it with the robotic arm. The CE study for OOS-RAV took place from 4th to 8th May 2015 in the Concurrent Engineering Facility of the DLR Bremen. The domains were occupied by members of various DLR sites depending on their expertise