Jose Felix Rojas

• University of the Basque Country

Using near-infrared observations of Neptune from the Keck and Lick Observatories, and the Hubble Space Telescope in combination with amateur datasets, we calculated the drift rates of prominent infrared-bright cloud features on Neptune between 2018 and 2021. These features had lifespans of $\sim 1$ day to $\geq$1 month and were located at mid-latit...

Context. A stellar occultation by Neptune’s main satellite, Triton, was observed on 5 October 2017 from Europe, North Africa, and the USA. We derived 90 light curves from this event, 42 of which yielded a central flash detection. Aims. We aimed at constraining Triton’s atmospheric structure and the seasonal variations of its atmospheric pressure si...

On May 31, 2020 a short-lived convective storm appeared in one of the small cyclones of Jupiter's South Temperate Belt (STB) at planetographic latitude 30.8°S. The outbreak was captured by amateur astronomer Clyde Foster in methane-band images, became widely known as Clyde's Spot, and was imaged at very high resolution by the Junocam instrument on...

A stellar occultation by Neptune's main satellite, Triton, was observed on 5 October 2017 from Europe, North Africa, and the USA. We derived 90 light curves from this event, 42 of which yielded a central flash detection. We aimed at constraining Triton's atmospheric structure and the seasonal variations of its atmospheric pressure since the Voyager...

Plain Language Summary Jupiter’s Great Red Spot (GRS) is a giant anticyclone with a length that has shrunk since 1879 from ∼ 40,000 km to its current value of 15,000 km. The GRS is the longest‐lived of all the planetary vortices, observed perhaps since the 17th century. During its history, the GRS has encountered a variety of smaller anticyclones a...

The transition region between the North Equatorial Band (NEBn) and North Tropical Zone (NTrZ) in Jupiter is home to convective storms, systems of cyclones and anticyclones and atmospheric waves. A large anticyclone formed in the year 2006 at planetographic latitude 19N and persists since then after a complex dynamic history, being possibly the thir...

The transition region between the North Equatorial Band (NEBn) and North Tropical Zone (NTrZ) in Jupiter is home to convective storms, systems of cyclones and anticyclones and atmospheric waves. Zonal winds are weak but have a strong latitudinal shear allowing the formation of cyclones (typically dark) and anticyclones (typically white) that remain...

Context: Until recently, camera networks designed for monitoring fireballs worldwide were not fully automated, implying that in case of a meteorite fall, the recovery campaign was rarely immediate. This was an important limiting factor as the most fragile - hence precious - meteorites must be recovered rapidly to avoid their alteration. Aims: To o...

Context. Until recently, camera networks designed for monitoring fireballs worldwide were not fully automated, implying that in case of a meteorite fall, the recovery campaign was rarely immediate. This was an important limiting factor as the most fragile – hence precious – meteorites must be recovered rapidly to avoid their alteration. Aims. The F...

Moist convective storms in Jupiter develop frequently and can trigger atmospheric activity of different scales, from localized storms to planetary-scale disturbances including convective activity confined inside a larger meteorological system. In February 2018 a series of convective storms erupted in Jupiter's South Temperate Belt (STB) (planetocen...

Moist convective storms in Jupiter develop frequently and can trigger atmospheric activity of different scales, from localized storms to planetary-scale disturbances including convective activity confined inside a larger meteorological system. In February 2018 a series of convective storms erupted in Jupiter’s South Temperate Belt (STB) (planetocen...

We examine Saturn's atmosphere with observations from ground-based telescopes and Hubble Space Telescope (HST). We present a detailed analysis of observations acquired during 2018. A system of polar storms that appeared in the planet in March 2018 and remained active with a complex phenomenology at least until Sept. is analyzed elsewhere (Sanchez-L...

We examine Saturn's atmospheric dynamics with observations in the visible range from ground-based telescopes and Hubble Space Telescope (HST). We present a detailed analysis of observations acquired during 2018 obtaining drift rates of major meteorological systems from the equator to the north polar hexagon. A system of polar storms that appeared i...

Context. Video observations of Jupiter obtained by amateur astronomers over the past 8 years have shown five flashes of light with durations of 1–2 s, each observed by at least two observers that were geographically separated. The first three of these events occurred on 3 June 2010, 20 August 2010, and 10 September 2012. Previous analyses of their...

Video observations of Jupiter obtained by amateur astronomers over the past eight years have shown five flashes of light of 1-2 s. The first three of these events occurred on 3 June 2010, 20 August 2010, and 10 September 2012. Previous analyses showed that they were caused by the impact of objects of 5-20 m in diameter, depending on their density,...

The zonal wind profile of Saturn has a unique structure at 60°N with a double-peaked jet that reaches maximum zonal velocities close to 100 ms⁻¹. In this region, a singular group of vortices consisting of a cyclone surrounded by two anticyclones was active since 2012 until the time of this report. Our observation demonstrates that vortices in Satur...

We provide measurements of the absolute reflectivity of Jupiter and Saturn along their central meridians in filters covering a wide range of visible and near-infrared wavelengths (from 0.38 to 1.7 $\mu$m) that are not often presented in the literature. We also give measurements of the geometric albedo of both planets and discuss the limb-darkening...

Since 2013, observations of Neptune with small telescopes have resulted in several detections of long-lived bright atmospheric features that have also been observed by large telescopes such as Keck II or Hubble. The combination of both types of images allows the study of the long term evolution of major cloud systems in the planet. In 2013 and 2014...

We provide measurements of the absolute reflectivity of Jupiter and Saturn along their central meridians in filters covering a wide range of visible and near-infrared wavelengths (from 0.38 to 1.7 $\mu$m) that are not often presented in the literature. We also give measurements of the geometric albedo of both planets and discuss the limb-darkening...

We present a methodology to analyse and interpret a set of telescopic observations of the mutual orbital phenomena between Jupiter's Galilean satellites (occultation and eclipses) as a practical teaching tool for photometry and astrodynamic studies in astronomy courses. The mutual phenomena we describe took place in 2014 and 2015 and the observatio...

Since 2013, observations of Neptune with small telescopes have resulted in several detections of long-lived bright atmospheric features that have also been observed by large telescopes such as Keck II or Hubble. The combination of both types of images allows the study of the long term evolution of major cloud systems in the planet. In 2013 and 2014...

We describe a huge planetary-scale disturbance in the highest-speed Jovian jet at latitude 23.5°N that was first observed in October 2016 during the Juno perijove-2 approach. An extraordinary outburst of four plumes was involved in the disturbance development. They were located in the range of planetographic latitudes from 22.2° to 23.0°N and moved...

We analyze Jupiter observations between December 2015 and August 2016 in the 0.38–1.7 μm wavelength range from the PlanetCam instrument at the 2.2 m telescope at Calar Alto Observatory and in the optical range by amateur observers contributing to the Planetary Virtual Observatory Laboratory. Over this time Jupiter was in a quiescent state without n...

Since 2003 the Planetary Virtual Observatory and Laboratory (PVOL) has been storing and serving publicly through its web site a large database of amateur observations of the Giant Planets (Hueso et al., 2010a). These images are used for scientific research of the atmospheric dynamics and cloud structure on these planets and constitute a powerful re...

Since 2003 the Planetary Virtual Observatory and Laboratory (PVOL) has been storing and serving publicly through its web site a large database of amateur observations of the Giant Planets (Hueso et al., 2010a). These images are used for scientific research of the atmospheric dynamics and cloud structure on these planets and constitute a powerful re...

We report Venus image observations around the two maximum elongations of the planet at June and October 2015. From these images we describe the global atmospheric dynamics and cloud morphology in the planet before the arrival of JAXA Akatsuki mission on December the 7th. The majority of the images were acquired at ultraviolet wavelengths (380-410 n...

We report Venus image observations around the two maximum elongations of the planet at June and October 2015. From these images we describe the global atmospheric dynamics and cloud morphology in the planet before the arrival of JAXA’s Akatsuki mission on December the 7th. The majority of the images were acquired at ultraviolet wavelengths (380-410...

Saturn has an intense and broad eastward equatorial jet with a complex three-dimensional structure mixed with time variability. The equatorial region experiences strong seasonal insolation variations enhanced by ring shadowing, and three of the six known giant planetary-scale storms have developed in it. These factors make Saturn's equator a natura...

We present PlanetCam UPV/EHU, an astronomical camera designed fundamentally for high-resolution imaging of Solar System planets using the "lucky imaging" technique. The camera observes in a wavelength range from 380 nm to 1.7 μm and the driving science themes are atmosphere dynamics and vertical cloud structure of Solar System planets. The design c...

In this work, a specific implementation of a so-called experimental or open-ended laboratory is proposed and evaluated. Keeping in mind the scheduling limitations imposed by the context, first-year engineering physics laboratory practices have been revised in order to facilitate acquisition of the skills that are required in the experimental work....

We investigate the long-term motion of Saturn's North-Pole Hexagon and the structure of its associated eastward jet, using Cassini ISS and ground-based images from 2008 to 2014. We show that both are persistent features that have survived the long polar night, the jet profile remaining essentially unchanged. During those years the hexagon vertices...

Context. The general circulation of Jupiter's atmosphere at cloud level is dominated by a system of zonal jets that alternate in direction with latitude. The winds, measured in high-resolution images obtained by different space missions and the Hubble Space Telescope, are overall stable in their latitude location with small changes in intensity at...

One of the most characteristic feature of Jupiter's atmosphere is its global wind structure which is characterized by strong zonal winds alternating in latitude and correlated with the bright Zones and dark Belts of the planet. This wind system presents a marked temporal stability although the structure of some of its bands change strongly in a qua...

PlanetCam is a two-channel fast-acquisition and low-noise camera designed for a multispectral study of the atmospheres of the planets (Venus, Mars, Jupiter, Saturn, Uranus and Neptune) and the satellite Titan at high temporal and spatial resolutions simultaneously invisible (0.4-1 μm) and NIR (1-2.5 μm) channels. This is accomplished by means of a...

PlanetCam is a two-channel camera designed primarily to observe the atmospheres of the planets (Venus, Mars, Jupiter, Saturn, Uranus and Neptune) and the satellite Titan simultaneously at visible (0.4-1 microns) and NIR (1-2.5 microns) wavelengths with high temporal and spatial resolution. This is accomplished by means of a dichroic beam splitter t...

Abstract The general circulation of Jupiter's atmosphere is dominated by a system of zonal winds alternating in latitude and related to the Bands and Zones structure of the planet. The zonal winds have been retrieved in several occasions by analyzing cloud motions in spacecraft observations of the planet and with HST observations [1,3,6,7]. In spit...

The South Equatorial Belt (SEB) of Jupiter is known to alternate its appearance at visible wavelengths from a classical belt-like band most of the time to a short-lived zone-like aspect which is called a “fade” of the belt, hereafter SEBF. The albedo change of the SEB is due to a change in the structure and properties of the clouds and upper hazes....

We emphasize the importance of treating Jupiter, its satellites and its magnetosphere as a system of mutual interactions and present a case for the multi-disciplinary investigation of that system. We point out (in a necessarily superflcial way) the need for further measurements of

Jupiter's South Equatorial Belt (SEB) is known to suffer global albedo changes with a not well defined period [1]. The transition from a "belt-like" aspect (low albedo at visible wavelengths) to a "zone-like" (bright albedo) is known as a "Fade". During 2009 the SEB suffered a fading process and became completely transformed to a zone by the first...

We present a summary of the activities undertaken over the first year of operations of the "Aula Espazio Gela Observatory", with teaching and astronomy outreach purposes. The observatory belongs to the Universidad del País Vasco and is a fundamental part of the "Master en Ciencia y Tecnología Espacial" (Space Science and Technology master). It is a...

We present a study of the equatorial region of Jupiter, between latitudes ∼15°S and ∼15°N, based on Cassini ISS images obtained during the Jupiter flyby at the end of 2000, and HST images acquired in May and July 2008. We examine the structure of the zonal wind profile and report the detection of significant longitudinal variations in the intensity...

The observation, characterization, and understanding of planetary atmospheres are key components of Solar System exploration. Their study requires, among other observations, the use of image data acquired from spacecrafts. The basic tasks that are generally used to work with planetary image data are: image navigation, projection, image processing,...

The Aula Espazio Gela is a facility at the School of Technical Engineering of the Universidad del Pais Vasco (Bilbao, Spain) dedicated to the education of undergarduated and gratuated students in the research and technology of space science activities. It also promotes the collaboration between the University and industrial spatial sector. One of t...

We have studied the equatorial region of Jupiter, between 15ºS and 15ºN, on Cassini ISS images obtained during the Jupiter flyby at the end of 2000 and on HST images acquired in May and July 2008. We have found significant longitudinal variations in the intensity of the 6ºN eastward jet, up to 60 m s-1 in Cassini and HST observations. In the HST ca...

The Atmospheres Node of the International Outer Planets Watch (IOPW, formerly known as International Jupiter Watch; Russell et al., 1990) intends to encourage and coordinate the imaging observations and study of the atmospheres of the Giant Planets. The main activity of the atmospheres node is to provide an interaction between the professional and...

In this work we show a study of the dynamics and clouds in the equatorial zone of Jupiter. The studied area is wider than the pure Equatorial Zone ranging from the southern limit of the South Equatorial Belt (SEB) to the northern limit of the North Equatorial Belt (NEB). We have used images from the Cassini flyby in December 2000 (wavelengths of 75...

A reanalysis of Galileo images of Jupiter's Equatorial Zone obtained in 1999 and 2001 reveals the presence of trains of cloud bands, probably generated by gravity waves, similar to those seen in Voyager 1 and 2 (1979) and New Horizons (2007) images. No such waves have been found in a similar analysis of the Cassini flyby (2000) dataset. We present...

We have measured the vertical shear of the zonal winds in the cloud-haze upper layer of Saturn using Cassini ISS images obtained in the filters MT2 (753 nm methane absorption band, sensitive to the upper haze) and CB2 (adjacent continuum, sensitive to the lower cloud). Our radiative transfer models indicate that at the eastward jet peaks these filt...

Up to the present, evidence of the vertical wind shear in Saturn at cloud level has been captured in the equatorial jet. For other regions the vertical shear of the zonal wind system above the main cloud deck of Saturn's atmosphere has been inferred from meridional temperature measurements at different altitudes by using the Cassini CIRS instrument...

The atmospheres of the gas giant planets (Jupiter and Saturn) contain jets that dominate the circulation at visible levels. The power source for these jets (solar radiation, internal heat, or both) and their vertical structure below the upper cloud are major open questions in the atmospheric circulation and meteorology of giant planets. Several obs...

We present in this work the study of the vertical cloud structure before, during and after the 2007 NTB Disturbance. We used Hubble Space Telescope observations of the three stages taken from the near ultraviolet (275 nm) to the near infrared (953 nm) in seven filters including the deep methane band at 890nm. Those images were complemented with gro...

Saturn's southern pole was observed at high resolution by the Cassini Imaging Science Subsystem (ISS) during the spacecraft insertion orbit in July 2004. Cloud tracking of individual features on images taken at a wavelength of 938 nm reveal the existence of a strong polar vortex enclosed by a jet with maximum speed of relative to System III rotatio...

We present a long-term study at visible wavelengths of the motions and spatial distribution of the hot spots at 7°N of Jupiter. This research involves seven years of observations of the planet between 1979 and 2002 and includes data from Voyagers 1 and 2, Hubble Space Telescope, and a number of ground-based observatories. Our analysis of the North...

We describe the temporal variability of the zonal jets of Jupiter and Saturn from a long-term systematic observation of motions at the upper cloud level. Globally, the pattern is highly stable but significant changes on the strongest eastward jets of each planet have been detected. The first one is the speed variability in the 180 m/s jet stream in...

The collaboration between amateurs astronomers and the professional community has been fruitful on many areas of astronomy. The development of the Internet has allowed a better than ever capability of sharing information worldwide and access to other observers data. For many years now the International Jupiter Watch (IJW) Atmospheric discipline has...

We present a study of the vertical structure of clouds and hazes in the upper atmosphere of Saturn's Southern Hemisphere during 1994–2003, about one third of a Saturn year, based on Hubble Space Telescope images. The photometrically calibrated WFPC2 images cover the spectral region between the near-UV (218–255 nm) and the near-IR (953–1042 nm), inc...

We use ground-based observations (going back to 1876), Pioneer-11 data (1979), Voyager 1 and 2 encounter images in 1980 and 1981, and HST 1990-2004 images, to study the changes that occurred in the vertical cloud structure and morphology and motions, in Saturn's Equatorial Region (approximately the band between latitudes 40 deg North and South). We...

We review our current understanding of the general circulation at cloud top levels in the atmospheres of the giant planets Jupiter and Saturn.

Analyses of Hubble Space Telescope (HST) images of Saturn obtained from August 2003 to March 2004, with extensive support from ground-based telescopes, have been used to characterize the cloud morphology and motions in its atmosphere few months before the Cassini encounter. We present data on the major meteorological features as potential targets f...

The knowledge of the vertical cloud structure and its temporal evolution of the giant planets is essential to understand some of the main properties of their atmospheres. Hubble Space Telescope images in the spectral region between near-UV (255 nm) to near-IR (1042 nm), including the 890 nm methane band, have been photometrically calibrated in orde...

The atmospheres of the giant planets Jupiter and Saturn have a puzzling system of zonal (east-west) winds alternating in latitude, with the broad and intense equatorial jets on Saturn having been observed previously to reach a velocity of about 470 m x s(-1) at cloud level. Globally, the location and intensity of Jupiter's jets are stable in time t...

In this work we present a photometric study of Saturn's Southern Hemisphere based on the Hubble Space telescope yearly campaigns from 1996 to 2002. More than a hundred images, mainly taken with the WFPC2 in a wide spectral coverage from 218nm to 1042nm, were calibrated in order to obtain the absolute reflectivity variations from limb to limb at sel...

We present a photometric study of Saturn’s Southern Polar Region based on Hubble Space Telescope images from 1997 to 2001 in a wide spectral coverage (218–1042 nm). A numerical model has been applied in order to obtain the vertical structure at different latitudes. We have constrained the optical properties of the atmospheric particles in addi­tion...

We present a photometric study of Saturn's Southern Hemisphere based on the Hubble Space Telescope yearly campaigns in the 1990's. Calibrated images taken with the WFPC2 in a wide spectral coverage (218nm-1042nm) were used in order to constrain the properties and the temporal changes of the atmospheric particles and the optical depths of clouds and...

We present a comparative observational perspective of unique phenomena that took place in recent years: the interaction and merger between the largest vortices present in the atmosphere of Jupiter.

We have used the HST-WFPC2 archived images of Jupiter in the period 1994-1998 together with a large set of CCD ground based images, to study the zonal distribution, long-term motions, lifetimes, interactions and other properties of the hot spot - plume regions at 7 degrees North. Red and near infrared filters covering the wavelength range 650 - 953...

During the 1998 Jupiter–Sun conjunction, the 60-year-old white ovals BC and DE at 33° south latitude merged into a larger oval “BE” at the same latitude (J. Lecacheux, P. Drossart, F. Colas, G. S. Orton, B. Fisher, A. Sanchez-Lavega, R. Hueso, J. F. Rojas, and I. Miyazaki, IAU Circular No. 6942). Here we report our study of the motions, morphology,...

A regular extensive CCD imaging of Saturn allowed us to analyze the discrete cloud activity in the Equatorial Zone from 1995 to 1997. The large-scale storm observed in 1994 at +10° ( and ) was rediscovered in 1995, reaching a lifetime >1 year. Its slow motion characterized by a zonal velocity difference of −150 ms−1 relative to background flow is c...

We present an analysis of new cloud motion measurements in Saturn's atmosphere from Voyager 1 and 2 images and define a nominal zonal wind velocity vs latitude profile for the cloud top level that can be used as reference for the upcoming Cassini mission. Improvements over previous studies include: (i) twice the number of wind vectors used, (ii) in...

A unique large-scale vortex, the White Tropical Oval (WTrO), was first observed in the South Tropical Zone of Jupiter, at the latitude of the Great Red Spot (GRS) in 1983. Its origin is probably related to a period of intense formation of eddies in the Southern edge of the South Equatorial Belt at latitude −20°. The WTrO survived many changes in th...

During Jupiter's last solar conjunction, the classical white ovals BC and DE changed into a single white oval, which we here label ``BE''. While the exact details are not known, pre-conjunction tracking showed BC and DE to be approaching each other, suggesting that their interaction resulted in the single remaining spot. We report here preliminary...

We present a two year study of the evolution of SL9 impact aerosol debris we observed between 0.4 and 0.9 micrometers with continuous high temporal coverage from July 1994 through September 1996 and at 1.7 and 2.3 micrometers during three observing runs in July 1994 and March and August 1995. Temporal cylindrical map projections at red continuum wa...

We present an overview of the studies we have performed of the unusual storm activity that is occurring in the Equatorial Zone (EZ) of Saturn since 1990 based on a long-term CCD imaging (261-953 nm).

We report on a new series of ground-based CCD observations at visual wavelengths, covering a period of 1255 days between May 1992 and November 1995, of the longest-lived asymmetric feature known in Saturn's atmosphere: the north polar spot (NPS). This completes our previous analysis of this feature during the period 1990–1991 (A. Sanchez-Lavega, J....

We report on a new series of CCD imaging obtained at Pic-du-Midi Obs. at red wavelengths (600-900 nm) of the longest-lived asymmetric feature in Saturn's atmosphere: the North Polar Spot (NPS).The observations covered a period of 1255 days spanning from May 1992 to November 1995. This completes our previous report on NPS data for the period 1990-19...

We introduce a general numerical simulation method that allows us to simulate different experimental conditions, getting the microcreep, elastic aftereffect and thermostimulated microdeformation curves. It also allows us to simulate the internal friction spectra vs. temperature in a similar way. The method is able to check the response of the mater...

Changes in belts and zones of Jupiter are sometimes virulent, starting from a localized eruption followed by the development of a planetary scale disturbance. The archetype of this phenomenology occurs rarely, about once every fifteen years, at 23° North latitude where the highest speed Jovian jet stream resides. In late March 2007 two nearly simul...

Historical ground-based and recent HST observations show that Saturn's Equatorial Atmosphere is the region where the most intense large-scale dynamical variability took place at cloud level in the planet. Large-scale convective storms (nicknamed the ``Great White Spots") occurred in 1876, 1933 and 1990. The best studied case (the 1990 storm), produ...

We report the analysis of images obtained by the contributors to the International Outer Planet Watch (IOPW) of the debris left in the atmosphere of Jupiter by the object that impacted the planet between 18 and 19 July 2009. The discovery images by Anthony Wesley in July 19.625 and the first two days of its tracking, shows a dark debris spot (conti...