arXiv subjects

Gregor Steinbrügge

Publications and source records attributed to Gregor Steinbrügge.

4 recordsLinked to original sources

arXiv2023

Observation of solar radio burst events from Mars orbit with the Shallow Radar instrument

Multispacecraft and multiwavelength observations of solar eruptions such as flares and coronal mass ejections are essential to understand the complex processes behind these events. The study of solar burst events in the radio-frequency spectrum has relied almost exclusively on data from ground-based observations and a few dedicated heliophysics missions such as STEREO or Wind. Reanalysing existing data from the Mars Reconnaissance Orbiter (MRO) Shallow Radar (SHARAD) instrument, a Martian planetary radar sounder, we have discovered the instrument was also capable of detecting solar radio bursts, and was able to do so with unprecedented resolution for a space-based solar instrument. In this study we aim at demonstrating the reliability and value of SHARAD as a new solar radio-observatory. We characterised the sensitivity of the instrument to type-III solar radio bursts through a statistical analysis of correlated observations, using STEREO and Wind as references. Using 38 correlated detections, we establish the conditions under which SHARAD can observe solar bursts in terms of acquisition geometry. As an example of scientific application, we also present the first analysis of type-III characteristic times at high resolution beyond 1 AU. A simple logistic model based purely on geometrical acquisition parameters can predict burst show vs. no-show in SHARAD data with an accuracy of 79.2%, demonstrating the reliability of the instrument for detecting solar bursts and laying the foundation for using SHARAD as a solar radio-observatory. The extremely high resolution of the instrument, both in temporal and frequency directions, its bandwidth, and its position in the solar system enable SHARAD to make significant contributions to heliophysics; it could inform on plasma processes on the site of the burst generation and along the propagation path of associated fast electron beams.

astro-ph.SR↗

arXiv2021

Prospects for Mapping Temporal Height Variations of the Seasonal CO2 Snow/Ice Caps at the Martian Poles by Co-registration of MOLA Profiles

We investigate the feasibility and demonstrate the merits of using Mars Orbiter Laser Altimeter (MOLA) profiles to retrieve seasonal height variations of CO2 snow/ice cap in Mars' polar areas by applying a co-registration strategy. We present a prototype analysis on the research region of [85.75°S, 86.25°S, 300°E, 330°E] that is located on the residual south polar cap. Our method comprises the recomputation of MOLA footprint coordinates with an updated Mars Global Surveyor (MGS) ephemeris and a revised Mars rotation model. The reprocessed MOLA dataset at the South Pole of Mars (poleward of 78°S) is then self-registered to form a coherent reference digital terrain model (DTM). We co-register segments of reprocessed MOLA profiles to the self-registered MOLA reference DTM to obtain the temporal height differences at either footprints or cross-overs. Subsequently, a two-step Regional Pseudo Cross-over Adjustment (RPCA) procedure is proposed and applied to post-correct the aforementioned temporal height differences for a temporal systematic bias and other residual errors. These pseudo cross-overs are formed by profile pairs that do not necessarily intersect, but are connected through the underlaying DTM. Finally, CO2 snow/ice temporal height variation is obtained by median-filtering those post-corrected temporal height differences. The precision of the derived height change time series is ~4.9 cm. The peak-to-peak height variation is estimated to be ~2 m. In addition, a pronounced "pit" (transient height accumulation) of ~0.5 m in magnitude centered at Ls=210° in southern spring is observed. The proposed method opens the possibility to map the seasonal CO2 snow/ice height variations at the entire North and South polar regions of Mars.

astro-ph.EP↗

arXiv2021

A Recipe for Geophysical Exploration of Enceladus

Orbital geophysical investigations of Enceladus are critical to understanding its energy balance. We identified key science questions for the geophysical exploration of Enceladus, answering which would support future assessment of Enceladus' astrobiological potential. Using a Bayesian framework, we explored how science requirements map to measurement requirements. We performed mission simulations to study the sensitivity of a single spacecraft and dual spacecraft configurations to static gravity and tidal Love numbers of Enceladus. We find that mapping Enceladus' gravity field, improving the accuracy of the physical libration amplitude, and measuring Enceladus' tidal response would provide critical constraints on the internal structure, and establish a framework for assessing Enceladus' long-term habitability. This kind of investigation could be carried out as part of a life search mission at little additional resource requirements.

astro-ph.IM↗

arXiv2017

The reference frames of Mercury after MESSENGER

We report on recent refinements and the current status for the rotational state models and the reference frame of the planet Mercury. We summarize the performed measurements of Mercury rotation based on terrestrial radar observations as well as data from the Mariner 10 and the MESSENGER missions. Further, we describe the different available definitions of reference systems for Mercury, which are realized using data obtained by instruments on board MESSENGER. In particular, we discuss the dynamical frame, the principal-axes frame, the ellipsoid frame, as well as the cartographic frame. We also describe the reference frame adopted by the MESSENGER science team for the release of their cartographic products and we provide expressions for transformations from this frame to the other reference frames.

astro-ph.EP↗