Venus surface roughness and Magellan stereo data

Presented are results of some studies to develop tools useful for the analysis of Venus surface shape and its roughness. Actual work was focused on Maxwell Montes. The analyses employ data acquired by means of NASA's Magellan satellite. The work is primarily concerned with deriving measurements of the Venusian surface using Magellan stereo SAR. Roughness was considered by means of a theoretical analyses based on digital elevation models (DEM's), on single Magellan radar images combined with radiometer data, and on the use of multiple overlapping Magellan radar images from cycles 1, 2, and 3, again combined with collateral radiometer data

Rapid pre-explosion increase in dome extrusion rate at La Soufrière, St. Vincent quantified from synthetic aperture radar backscatter

The extrusion rate of a lava dome is a critical parameter for monitoring silicic eruptions and forecasting their development. Satellite radar backscatter can provide unique information about dome growth during a volcanic eruption when other datasets (e.g., optical, thermal, ground-based measurements, etc.) may be limited. Here, we present an approach for estimating volcanic topography from individual backscatter images. Using data from multiple SAR sensors we apply the method to the dome growth during the 2021 eruption at La Soufrière, St. Vincent. We measure an average extrusion rate of 1.8 m³s¯¹ between December 2020 and March 2021 before an acceleration in extrusion rate to 17.5 m³s¯¹ in the 2 days prior to the explosive eruption on 9 April 2021. We estimate a final dome volume of 19.4 million m³, extrapolated from the SAR sensors, with approximately 15% of the total extruded volume emplaced in the last 2 days. A possible explanation for the acceleration in extrusion rate could be the combined emptying of a conduit and reservoir of older material before the ascent of gas-rich magma in April 2021

Recent Changes to Langjökull Icecap, Iceland: An investigation integrating airborne LiDAR and satellite imagery

Langjökull, Iceland’s second largest icecap (~950 km$^{2}$), was the subject of an incomplete airborne LiDAR survey in August 2007. This study investigates and evaluates the application of photoclinometry, which employs visible light imagery (here, Landsat ETM+ band 4) to interpolate unmeasured sections of this fragmented data set. A complete digital elevation model (DEM) of Langjökull was produced, and photoclinometry was determined to be a satisfactory and robust technique for topographic interpolation (RMS error = 3.4 m over a 3 km section). Future applications of photoclinometry can ensure optimal results by focusing on the consistent ability of their imager to accurately represent low contrast surfaces; also, consideration of setting characteristic such as solar azimuth, solar elevation, and moderate surface slope will make photoclinometric interpolation more effective. Photoclinometry it is proven to be a current and valuable technique, it is confirmed as a secondary rather than primary tool, and other possible applications of photoclinometry are considered. Using the completed DEM of Langjökull for summer 2007 and a previously prepared corresponding 1997 data set, Langjökull was found to have a specific annual mass balance of -0.99$\pm$0.1 meters per year of water equivalence (m yr$^{-1}$ w.e.), a number which confirms published predictions that Langjökull will likely disappear in the next 200 years. Comparison of remotely-sensed mass balance values and traditional $\textit{in situ}$ measurements revealed a possible systematic disparity; it is hypothesized that field measurements may not be sufficiently constraining behavior of interior areas and that the signal from strongly receding outlet glaciers may be skewing the $\textit{in situ}$ mass balance value calculated for the entire icecap. An additional DEM of outlet Hagafellsjökull Vestari allowed for calculation of specific mass balances of -2.28 m yr$^{-1}$ w.e. for 1997-2001, -3.86 m yr$^{-1}$ w.e. for 2001-2007, and -3.23 m yr$^{-1}$ w.e. for 1997-2007. Similarly, visual inspection and tracing of Landsat images showed a recession of -3.42.5 km$^{2}$ yr$^{-1}$ from 1994 to 2007. The new 2007 DEM allowed for clear visualization of strong recession on several Langjökull outlets as well as interior mass loss and terminus advance witnessing to the 1998 surge event of outlet Hagafellsjökull Eystri. In addition, slight interior elevation increase and anti-correlated mass loss and terminal retreat potentially indicate a future surge of outlet Hagafellsjökull Vestari. In sum, the technological and glaciological information put forward in this study provides a method for innovative cryospheric research, presents a much needed benchmark and update on the state of Langjökull, and ultimately facilitates and encourages continued monitoring of highly important smaller glaciers and icecaps

Google the earth: what's next?

Sensing the Earth has proven to be a tremendously valuable tool for understanding the world around us. Over the last half-century, we have built a sophisticated network of satellites, aircraft, and ground-based remote sensing systems to provide raw information from which we derive and improve our knowledge of the Earth and its phenomena. Through remote sensing, our basic scientific knowledge of the Earth and how it functions has expanded rapidly in the last few decades. Applications of this knowledge, from natural hazard prediction to resource management, have already proven their benefit to society many times over. Today maps and satellite imageries have become an integral part of the developmental process and have also triggered new business opportunities. Maps are essential at all stages of infrastructure development, resource planning and the disaster management cycle. Satellite imagery/data can be used for everything from ground truthing and change detection, to more sophisticated analyses, including feature extraction and natural hazard prediction. As imagery has become more accessible and more affordable in recent years, there is also a growing convergence of imagery and geographic information system (GIS) applications. Geospatial scientists and analysts thus, need to be able to easily access imagery and move seamlessly between GIS and image processing applications to derive the most information possible from them. Technologically, the challenge is to design sensors that exhibit high sensitivity to the parameters of interest while minimizing instrument noise and impacts of other natural variables. The scientific challenge is to develop retrieval algorithms that describe the physical measurement process in sufficient detail, yet are simple enough to allow robust inversion of the remotely sensed signals. Considering the exponential growth of data volumes driven by the rapid progress in sensor and computer technologies in recent years, the future of remotely sensed data should ideally be in automated data processing, development of robust and transferable algorithms and processing chains that require little or no human intervention. In meeting the above mentioned challenges, some research works have been done at Universiti Putra Malaysia. These works cover all aspects of the remote sensing process, from instrument design, image processing, image analysis to the retrieval of geophysical parameters and their application in natural resources planning and disaster management. Some of the major research efforts include feature extraction from satellite imagery; spatial decision support system for oil spill detection, monitoring and contingency planning; fish forecasting; UAV-based remote imaging and natural disaster management and early warning systems for floods and landslides. This lecture concludes that through remote sensing, our basic scientific knowledge of the Earth and how it functions have expanded rapidly in the last few decades. Applications of this knowledge, from natural hazard prediction to resource management, have already proven to be beneficial to society many times over. As the demand for even faster, better and more temporally and spatially variable information grows dramatically, this lectures answers the question of what remote sensing will be like in the coming decades and the new capabilities and challenges that will emerg

Directory of research projects, 1991. Planetary geology and geophysics program

Information is provided about currently funded scientific research within the Planetary Geology and Geophysics Program. The directory consists of the proposal summary sheet from each proposal funded by the program during fiscal year 1991. Information is provided on the research topic, principal investigator, institution, summary of research objectives, past accomplishments, and proposed investigators

Directory of research projects: Planetary geology and geophysics program

Information about currently funded scientific research within the Planetary Geology and Geophysics Program is provided, including the proposal summary sheet from each proposal funded under the program during fiscal year 1990. Information about the research project, including title, principal investigator, institution, summary of research objectives, past accomplishments, and proposed new investigations is also provided

Reports of planetary geology and geophysics program, 1987

This is a compilation of abstracts of reports from Principal Investigators of NASA's PLanetary Geology and Geophysics program, Office of Space Science and Applications. The purpose is to document in summary form research work conducted in this program during 1987. Each report reflects significant accomplishments in the area of the author's funded grant or contract

Comparative study of the diachronic evolution of the geological and volcanological environments of the earth with the saturnian satellites Titan and Enceladus.

This thesis presents on the study of the environment of Titan and Enceladus, Saturn’s satellites observed by the Cassini-Huygens mission. Various aspects of the geology of Titan are presented focusing on the characteristics of the surface geological features and processes,the internal structure and the correlation with the atmosphere. The morphotectonic features are presented on the basis of terrestrial models. Moreover, Titan areas probably correlated with the interior are tested against a geophysical model of tidal distortion and found to conform with localisation and internal dynamics. We then study the surface albedo and composition of specific Titan areas (Hotei Regio, Tui Regio, Sotra Patera) –determined by the PCA method- based on data from Cassini/VIMS (0.4–5 μm) on which a radiative transfer code is applied with the most updated spectroscopic parameters. Monitoring of these areas showed surface albedo changes in the course of 1-3.5 yrs, implying dynamic exogenic-endogenic processes that affect the surface and compatible with cryovolcanism in the case of Sotra Patera. Processes that form the surface of Enceladus are also discussed. In addition, the analogies with the Earth's surface and possible internal processes on the icy satellites are being explored. The astrobiological implications of this work are discussed within the framework of the quest for habitable environments in our outer Solar system. These studies are related to the preparation of future space missions to the systems of Jupiter and Saturn and payload capability. Finally, public awareness and perspectives of this research are discussed

Comparative study of the diachronic evolution of the geological and volcanological environments of the Earth and the Saturnian satellites, Titan and Enceladus

Η παρούσα διδακτορική διατριβή αφορά τη μελέτη των περιβαλλόντων του Τιτάνα και του Εγκέλαδου, δορυφόρων του Κρόνου, μέσω της ανάλυσης δεδομένων που ανακτήθηκαν από τη διαστημική αποστολή Cassini-Huygens. Αρχικά παρουσιάζεται η επισκόπηση της γεωλογίας του Τιτάνα, με επίκεντρο τις γεωλογικές δομές και διεργασίες και το συσχετισμό μεταξύ της ατμόσφαιρας, της επιφάνειας και του εσωτερικού του δορυφόρου. Οι μορφοτεκτονικές δομές κατατάσσονται σε συγκεκριμένες κατηγορίες βάσει γήινων μοντέλων σχηματισμού. Επιφανειακές περιοχές του Τιτάνα, οι οποίες θεωρούνται συνδεδεμένες με το εσωτερικό, συγκρίθηκαν με γεωφυσικά μοντέλα παλιρροιακής στρέβλωσης και διαπιστώθηκε ότι συμπίπτουν σε σχέση με τη θέση, την επιφάνεια και την εσωτερική ενεργότητα. Ένα δεύτερο μέρος της διδακτορικής διατριβής παρουσιάζει την ενδελεχή ανάλυση συγκεκριμένων περιοχών του Τιτάνα –όπως αυτές καθορίζονται μέσω μιας στατιστικής μεθόδου– με επίκεντρο την επιφανειακή ανακλαστικότητα που παρουσιάζουν και τη χημική σύνθεση από την επεξεργασία δεδομένων του φασματογράφου Cassini/VIMS (εγγύς υπέρυθρη περιοχή του φάσματος από 0,4 έως 5 micron). Η εφαρμογή ενός εκσυγχρονισμένου και state-of-the-art κώδικα μεταφοράς ακτινοβολίας, επέδειξε τη φασματική συμπεριφορά και το εύρος της φωτεινότητας αυτών των περιοχών. Η έρευνα τριών σημαντικών περιοχών, που έχουν προταθεί ως υποψήφιες κρυοηφαιστειακές (Hotei Regio, Tui Regio και Sotra Patera), παρουσίασε ενδείξεις χρονικής μεταβολής της επιφανειακής ανακλαστικότητας για δύο από αυτές σε μια χρονική περίοδο από 1-3,5 χρόνια, υποδεικνύοντας δυναμικές εξωγενείς - ενδογενείς διεργασίες, οι οποίες επηρεάζουν την επιφάνεια και είναι συμβατές με φαινόμενα κρυοηφαιστεότητας στην περίπτωση της Sotra Patera. Επίσης, οι διαδικασίες που σχηματίζουν την επιφάνεια του Εγκέλαδου περιγράφονται λεπτομερειακά στη διατριβή. Σε ένα τρίτο μέρος, γήινα ανάλογα επιφανειακών εμφανίσεων καθώς και διεργασιών παρουσιάζονται εκτεταμένα, επισημαίνοντας ενδιαφέρουσες ομοιότητες και διαφορές μεταξύ της πυριτικής Γης και των παγωμένων δορυφόρων. Οι αστροβιολογικές συσχετίσεις αυτής της εργασίας διεξάγονται στο πλαίσιο της αναζήτησης περιβαλλόντων κατοικησιμότητας στο εξωτερικό ηλιακό σύστημα. Όλες οι προαναφερθείσες μελέτες συνδέονται με την προετοιμα σία των μελλοντικών διαστημικών αποστολών και των οργάνων τους στα συστήματα του Κρόνου και του Δία. Τέλος, συζητούνται οι δυνατότητες εκλαΐκευσης της επιστήμης και οι προοπτικές που παρουσιάζει η συγκεκριμένη έρευνα.This thesis presents on the study of the environment of Titan and Enceladus, Saturn’s satellites observed by the Cassini-Huygens mission. Various aspects of the geology of Titan are presented focusing on the characteristics of the surface geological features and processes,the internal structure and the correlation with the atmosphere. The morphotectonic features are presented on the basis of terrestrial models. Moreover, Titan areas probably correlated with the interior are tested against a geophysical model of tidal distortion and found to conform with localisation and internal dynamics. We then study the surface albedo and composition of specific Titan areas (Hotei Regio, Tui Regio, Sotra Patera) –determined by the PCA method- based on data from Cassini/VIMS (0.4–5 μm) on which a radiative transfer code is applied with the most updated spectroscopic parameters. Monitoring of these areas showed surface albedo changes in the course of 1-3.5 yrs, implying dynamic exogenic-endogenic processes that affect the surface and compatible with cryovolcanism in the case of Sotra Patera. Processes that form the surface of Enceladus are also discussed. In addition, the analogies with the Earth's surface and possible internal processes on the icy satellites are being explored. The astrobiological implications of this work are discussed within the framework of the quest for habitable environments in our outer Solar system. These studies are related to the preparation of future space missions to the systems of Jupiter and Saturn and payload capability. Finally, public awareness and perspectives of this research are discussed