JuanCastillo29/space-mission-intelligence-data huggingface dataset:
O. J. White1, G. Molera Calvés1, and J. Edwards1 1 School of Natural Sciences, University of Tasmania, Hobart, 7000, TAS, Australia
Summary: The Jupiter Icy Moons Explorer (JUICE) spacecraft is a European Space Agency (ESA) mission to study the Jovian system, currently undergoing an eight-year cruise phase. The Planetary Radio Interferometric and Doppler Experiment (PRIDE) is one of eleven experiments contributing to the JUICE mission. PRIDE aims to conduct radio science experiments using ground-based radio telescopes, through both single dish and Very Long Baseline Interferometry (VLBI) observations. The University of Tasmania (UTAS) is an important contributor to PRIDE and JUICE, though its continental-wide network of radio telescopes in Australia. Over 35 PRIDE observations of JUICE were conducted during the period 2023-24, which enabled detailed analysis of space weather activity in this period, as well as the Lunar-Earth flyby campaign in August 2024. In this paper, we describe PRIDE VLBI observations of JUICE, and the first successful results of PRIDE with the University of Tasmania infrastructure.
Keywords:  Spacecraft Tracking, Space Weather, VLBI, JUICE, PRIDE.
Radio interferometric techniques applied to spacecraft tracking yield estimates of the relative velocity and positions of the spacecraft with respect of the ground stations. If the position of the ground stations is known accurately then these values can be derived for the spacecraft. This section draws from the explanations given in previous radio interferometric studies [5, 6, 7, 8].
Three main data types can be determined from radio observations of spacecraft telemetry: spacecraft range, Doppler shift and interferometric measurements. In the typical mode of operation for VLBI observations, ground stations transmit an uplink signal to a spacecraft, which lock and track it using a phase-locked loop (PLL). This is then phase modulated onto a downlink signal with a fixed frequency ratio. For example, in the C/X-band spacecraft commonly have an uplink frequency of 7145-7190 MHz and a downlink of 8400-8450 MHz [9].
The Doppler shift is the change in frequency between the transmitted and received signal due to the relative motion of the spacecraft (after accounting for the frequency offset of the uplink and downlink signals). This is given by Eqn 1.
Δ𝑓= (𝑟̇/𝑐)𝑓t,
(1) where 𝑟̇ is the spacecraft’s instantaneous range rate. This directly yields the spacecraft’s radial velocity from the line of sight of the ground station.
There are three different ways in which the signal can be transmitted and received; one-way, two-way and three-way mode, the latter of which is used for PRIDE observations. Three-way mode operates by having two ground stations used, one for transmission and another for reception of the spacecraft signal. Therefore, independent frequency standards are used at the two ground stations, typically hydrogen masers.
Four PRIDE VLBI observations were conducted of JUICE in the July-August 2024 period preceding the Lunar-Earth flyby, on July 2nd, August 3rd, 13th and 19th. The fringe finder and phase reference sources used for each observation are listed in Table 2.

[Table: Table 2: Radio sources used for PRIDE VLBI observations. The flux densities are
approximate, obtained from the Astrogeo Center, given in Janskys.]
We have implemented pipelines for various components of the PRIDE VLBI technique at UTAS. The scheduling and observing techniques using the UTAS antennas have been fully implemented, along with the correlation component of the data processing pipeline. Four experiments were conducted for the JUICE spacecraft during July-August 2024. Additionally, 35+ PRIDE Doppler experiments were conducted in the 2023-2024 period, which will enable analysis of the spacecraft’s space weather environment. The last step in producing the desired data output of the spacecraft radio images and determination of the state vectors is in analysing the correlator output in CASA or AIPS. With the assistance of Dr Sándor Frey and Dr Ross Burns these images were produced using AIPS, with the full data processing achieved in only three months despite the complexity of the VLBI technique and the various software packages used. A goal of future research at UTAS will be to process the data using CASA.
, E. Hauber

1Dpto. Física Aplicada I, EIB, Universidad País Vasco UPV/EHU, Bilbao, Spain
2Aula EspaZio Gela, Escuela de Ingeniería
3European Space Agency, ESAC, Madrid, Spain
4Instituto
de Bilbao, Universidad del País Vasco UPV/EHU, Bilbao, Spain
5Laboratory for Atmospheric and Space
de Astrofísica e Ciências do Espaço, Obs. Astronomico de Lisboa, Portugal
6German Aerospace Center (DLR), Institute of Planetary Research, Berlin,
Physics, University of Colorado, Boulder, USA
7Institut d’Astrophysique Spatiale, CNRS/University Paris Sud, Orsay, France
8European Space Agency, ESOC,
Germany.
9European Space Agency, ESTEC, Noordwijk,  The Netherlands
10Freie Universitaet Berlin, Institute
Darmstadt, Germany of Geological Sciences, Berlin, Germany
This cloud repeatedly forms in the early mornings, and repeats in a daily cycle between
Ls 220º and 320º every martian year.

[Figure: Figure 1. The elongated cloud extending around 1800 km to the west from Arsia Mons volcano on October 10 2018 (MY34). Image acquired by the VMC camera on board MEX. ESA press release: http://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Mars_Express_keeps_a n_eye_on_curious_cloud]
We report a previously unnoticed annually repeating phenomenon consisting of the daily formation of an extremely elongated cloud extending as far as 1800 km westward from Arsia Mons. It takes place in the Solar Longitude (Ls) range of ~220º-320º, around the Southern solstice. We study this Arsia Mons Elongated Cloud (AMEC) using images from different orbiters, including ESA Mars Express, NASA MAVEN, Viking 2, MRO, and ISRO Mars Orbiter Mission (MOM). We study the AMEC in detail in Martian Year (MY) 34 in terms of Local Time and Ls and find that it exhibits a very rapid daily cycle: the cloud growth starts before sunrise on the western slope of the volcano, followed by a westward expansion that lasts 2.5 hours with a velocity of around 170 m/s in the mesosphere (~45 km over the areoid). The cloud formation then ceases, it detaches from its formation point, and continues moving westward until it evaporates before the afternoon, when most sun-synchronous orbiters observe. Moreover we comparatively study observations from different years (i.e. MYs 29-34) in search of interannual variations and find that in MY33 the cloud exhibits lower activity, whilst in MY34 the beginning of its formation was delayed compared to other years, most likely due to the Global Dust Storm. This phenomenon takes place in a season known for the general lack of clouds on Mars. In this paper we focus on observations, and a theoretical interpretation will be the subject of a separate paper.
In September and October 2018 the Visual Monitoring Camera on board Mars Express observed a spectacular water ice cloud extending as far as 1800 km westward from the Arsia Mons Volcano on Mars. This curious extremely elongated cloud caught the attention of the public (http://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Mars_Ex press_keeps_an_eye_on_curious_cloud). We study this Arsia Mons Elongated Cloud (AMEC) with the aid of several instruments orbiting Mars. We find that the AMEC repeated regularly each morning for a number of months, and that it is an annually-repeating phenomenon that takes place every Martian Year around the southern hemisphere spring and summer. The AMEC follows a rapid daily cycle: it starts to expand from Arsia Mons at dawn at an altitude of about ~45 km, and for ~2.5 hours it expands westward as fast as 170 m/s (around 600 km/h). The cloud then detaches from Arsia Mons and evaporates before noon. In previous Martian Years, few observations of this phenomenon are available because most cameras orbiting Mars are placed in orbits where they can only observe during the afternoon, whereas this cloud takes place in the early morning, when observational coverage is much lower.
Water ice clouds are present throughout the Martian Year (MY) with large temporal and spatial variability (Wang & Ingersoll, 2002; Clancy et al., 2017; Wolff et al. 2019). They have been observed from ground-based telescopes (Herschel, 1784; Slipher, 1927; Smith & Smith 1972), orbiting spacecraft (Leovy et al., 1971;1973; Curran et al., 1973) and rovers (Kloos, 2016; Wolff et al., 2005).
Prominent clouds are commonly found in the region of Tharsis, and have been noticed since the telescopic era (Slipher, 1927; Smith & Smith, 1972). Based on early topographic maps, Sagan et al. (1971) proposed a topographic origin for these clouds over Tharsis and other high altitude regions. The observations of the Mariner and Viking missions supported this idea and confirmed the water ice composition (Peale et al., 1973; Curran et al., 1973). More recently Michaels et al. (2006) have shown in a mesoscale model how the circulation induced by giant volcanoes injects large amounts of aerosols into the global circulation.
Water ice clouds on Mars, including the topographic ones, are most commonly seen as part of the Aphelion Cloud Belt (ACB) in the season around Solar Longitude (Ls) 40º-140º (Clancy et al., 1996; 2017; James et al., 1996). Benson et al. (2003, 2006) studied the seasonal distribution of clouds around the giant volcanoes on Mars using afternoon observations, and found that the volcanoes usually lack clouds during the dusty season, in the Ls range ~200º-360º. Arsia Mons is an exception to this, as it shows cloud activity in the Ls range 245º-322º, while in general little cloud activity is found on Mars in this season (Benson et al. 2003, 2006; Wang & Ingersoll, 2002).
There is a bias in the local time of observations made by orbiting spacecraft that could affect our knowledge of the life cycle of Martian water ice cloud systems, which is that most observations in the past two decades of Mars exploration have been acquired by spacecraft in afternoon sunsynchronous orbits (whose observations are centered at local afternoon). This is the case for the Mars Global Surveyor (MGS), Mars Odyssey (later shifted to 7AM-7PM local times; Smith, 2019a), and Mars Reconnaissance Orbiter (MRO). Until 2014, when MAVEN (Mars Atmosphere and Volatile EvolutioN) and the Mars Orbiter Mission (MOM) arrived at Mars, Mars Express (MEX) was the only mission in a non-sun-synchronous orbit. The ExoMars Trace Gas Orbiter (TGO), which arrived in 2016 and began science operations in 2018, is also in a nonsun-synchronous orbit.
state of the atmosphere in different MYs (Sánchez-Lavega et al., 2018b). We note that 2018 observations of the AMEC were after the Martian Global Dust Storm of 2018 (GDS 2018; Sánchez-Lavega et al., 2019, Guzewich et al., 2019), and Global Dust Storms are the most conspicuous Martian events that exhibit interannual variability. In fact, Benson et al. (2006), based on afternoon observations, reported lower cloud activity over Arsia Mons following the 2001 GDS, compared to the previous MY.

In this first paper, we analyze observations of the Arsia Mons Elongated Cloud (AMEC). We start our analysis by focusing on MY 34 (which corresponds to observations in 2018), as most available observations of the AMEC correspond to this year. Then, we compare the characteristics of the AMEC in MY 34 with all available observations from previous years, in search of interannual variations. A theoretical analysis of the phenomenon will be the subject of a separate paper.
In section 2, we describe our Observations and Methods. In section 3, we briefly describe the Tharsis region and the topographic profiles of the four giant volcanoes, including Arsia Mons. In section 4, we describe the daily cycle followed by the AMEC, from twilight to noon and afternoon, as inferred from observations in MY34. In section 5, we show several morphologic and dynamic features of the cloud and describe its seasonal evolution. In section 6, we measure the altitude of the cloud. In section 7, we compare MY34 with observations from previous years, with a special interest in  interannual variations. Finally, in section 8 we summarize our observations and present our conclusions.

| Instrument | Spacecraft | Number of observations | Spatial resolution (km px-1) | MY |
| --- | --- | --- | --- | --- |
| VMC | MEX | 63 | 12 | 29,30,31,33,34 |
| HRSC | MEX | 3 | 1 | 33,34 |
| OMEGA | MEX | 1 | 5 | 34 |
| IUVS | MAVEN | 29 | 10 | 34 |
| MCC | MOM | 3 | 1 | 32 |
| VIS | Viking 2 | 2 | 1 | 12 |
| MARCI | MRO | * | 1 | * |
The most prominent volcanic provinces on Mars are the Elysium region, Alba Mons, and the Tharsis Region, which contains the four tallest volcanoes on Mars: Olympus Mons, Ascraeus Mons, Pavonis Mons, and Arsia Mons (Figure 4). The entire Tharsis areais considerably higher than the mean altitude of the Martian surface.

[Figure: Figure 4 shows a topographic map and the vertical profiles along the central axis of the four Tharsis volcanos. The summits of the four volcanos are 8-20 km above their surrounding area, and at their base they extend  300-500 km in diameter. All of the volcanoes also have depressed calderas in the range of 50-100 km in diameter and 1-4 km in depth.]

[Figure: Figure 4. Topography of the Tharsis region from MOLA-HSRC data plot with hillshading (Fergason et al., 2018). The four giant volcanoes are apparent. Right panels show topographic profiles for each volcano from MOLA. Altitudes are relative to the areoid.]
The AMEC daily cycle was observed in detail in MY34. In the Ls range 242º-296º, the AMEC was always present in the early morning. The first observation of the AMEC was performed by IUVS on September 2, 2018 (Ls 242º).

Prior to that date, the cloud was not present in suitable observations by VMC in August, in the Ls range 223-235º.  The last image of the AMEC was obtained by VMC on November 28 (Ls 296º) and the region was not observed by VMC later in the season. Orbital and operational constraints prevented observations of Arsia Mons by MAVEN after Ls ~260º. While more than 80 Martian sols separate the first and last observations, the AMEC phenomenon is likely to have started earlier (sometime between Ls 235º, when there is a negative observation, and Ls 242º, when there is a positive observation) and to have continued later than Ls 296º, since it was observed in an equivalent season in previous years (Fig. 2).

[Figure: Figure 5. Daily cycle of the AMEC in MY34. Top panel: Phases of the cloud evolution and instrument coverage as a function of LTST indicated in Martian hours. Transition time between phases is represented at a fixed time for simplicity, but there is obviously a degree of sol-to-sol variability, see main text for details. Local Times of the images in the bottom panel are 11]
VMC images of Arsia Mons taken some minutes before sunrise show the formation of a “twilight cloud” west of the volcano caldera, at ~237º E and 9.5º S  (Fig. 5a). The cloud forms during the nighttime, and sunlight starts illuminating the cloud tops before sunrise because of their altitude of 30±5 km above the Martian areoid (Hernández-Bernal et al., 2018). Diffuse hazes extending to the south of the cloud accompany the head during this twilight phase (Fig 5a).

[Figure: Figure 6. Expansion phase of the AMEC. (a) Length of the cloud as a function of LTST. Point incertainties are calculated as explained in Supplementary Text S3 . For long observations, only a representative part of all the available images are represented, separated by 15min. Linear fit (early anomalies excluded) gives an expansion velocity of 170 ± 10 ms-1; (b) Cloud trajectories (traced manually) on a topographic map, the same map as seen in Fig. 4. Color codes indicate the Ls ranges given in the legend in panel (a).]
For ~3 hours after the sunrise, the cloud grows rapidly in length forming the AMEC phenomenon (Figure 5b,c). We measured the length of the cloud (following its curvature) from available VMC images throughout the season and corresponding to different local times (Figure 6). When a VMC series was long enough, we measured several images in the series, always separated by at least 15 minutes to make sure that variation between images was significant.

[Figure: Figure 6a shows tail length against local time (from 6 to 8.5 h LTST). Only observations where the whole cloud is visible are included (discarding those images where the cloud penetrates the terminator). The growth is approximately linear, and a linear fit gives an apparent expansion velocity of 170 ± 10ms-1 . Assuming a constant rate, and considering the initial size of the head to be around 125km (see section 5.1), the linear fit indicates that the expansion from that size initiates at around 5.8±0.2 LTST (the local sunrise is at 5.7 LTST). The maximum length of the AMEC was measured on October 10 (Ls 266º), with a tail of around 1800 km in length.]

In some of the early sols (September 2018), the cloud was shorter than the value expected at the corresponding local time from the general trend, pointing towards some sol-to-sol and/or seasonal variability. These early anomalies are indicated by diamonds in Figure 6a, and could be due to the fact that the GDS 2018 was in its decaying stage throughout that period (Guzewich et al., 2019).

[Figure: Figure 6b illustrates the extension of the cloud tail at different local times and epochs. The concavity of the curved trajectories is always to the north, suggesting advection of the cloud by persistent combined zonal (westward) and meridional (northward) winds. Due to variations of existing winds, the curvature of the tail varies from sol-to-sol, with local time, and with Ls.]
At some point around 8.3-8.7 LTST the cloud detaches from its formation point in Arsia Mons. For example, we see the the cloud attached at 8.4 LTST in Fig 5c,  and already detached at later local times in Figs 5d and 5e. Some VMC images show that the cloud head narrows before its detachment (Figure 5c, supplementary animation S3), and IUVS observations capture detached clouds after 8.7 LTST (Figure 5d). At the beginning of this phase, there is no remnant cloud activity in the vicinity of Arsia Mons, as the whole cloud moves away from the volcano. Figure 7 shows the distance of the head of the cloud from the location on Arsia Mons where it formed, as measured in IUVS and VMC images.

It shows a linear trend, with large dispersion indicating sol-to-sol variability. A linear fit gives a detachment velocity of 150 ± 30 ms-1. All observations represented in this graph were acquired before Ls 260º, that is, in the period of the early anomalies mentioned in section 4.2 since due to limited coverage, there are no images of a detached cloud later in the season.
As the sol progresses, both IUVS and VMC observations of the detached cloud reveal a fainter and more turbulent elongated cloud (Figures 5e and 5f). The AMEC eventually disappears, and is no longer visible in IUVS observations at 13 LTST.

[Figure: Figure 7. Distance of the cloud head to Arsia Mons as a function of LTST during the detachment phase. Point uncertainties are calculated as in Figure 6a. Circles correspond to three measurements within the same VMC observation. Squares represent IUVS observations, each corresponding to a different sol. Due to the coverage limitations, all these observations correspond to the Ls range 240º-260º.]
As the head of the AMEC continues to move away from the base of the volcano, new clouds form over Arsia Mons. A few IUVS images show the development of faint clouds on the western slope of the volcano as early as 9.3 LTST (Figure 5d), but most clouds develop after 11 LTST, and they continue to be present until the last IUVS observation at 15.7 LTST (Figures 5h and 5i). Higher resolution images obtained by MARCI at around 14.0 LTST also show those clouds (Figure 5g). These afternoon clouds appearing around Arsia Mons in this season were also reported in Wang & Ingersoll (2003)

and Benson et al. (2003, 2006) and might not be related to the AMEC elongated cloud.
We measured the position and size of the head of the cloud throughout different local times and sols (Ls) in VMC images (Figure 8a-b). Error was estimated manually, taking into account the limited quality of the images and the diffuse boundaries of the clouds. Approximating the eastern boundary of the head to a semicircle, we determined its diameter and center, and used them as a measure of size and location respectively. Examples of actual head morphologies can be found in Figure 9. The head diameter ranged from 50 to 250 km with a typical value of about 125 km. Because of the dispersion of the data, it is difficult to retrieve a clear temporal evolution of the head size as a function of LTST or Ls (Figure 8c-d). There are hints of a quick head formation early in the morning, reaching a maximum size of ~175 km at 7 LTST, and then decreasing to around 75-100 km at 8.5 LTST, with no clear trend as the season evolves.

[Figure: Figure 8. Panels a and b: Position and size of the head of the AMEC as a function of LTST and Solar Longitude. The curves (traced manually) represent the head contour and colors identify LTST in (a) and Ls in (b). Panels (c) and (d) Head diameter as a function of LTST and Ls. (e) Latitude of the head center as a function of LTST. (f) Longitude of the head center as a function of Ls.]

The central latitude of the head was most often in the range 8.5º-10º S, within the range of latitudes of the Arsia Mons caldera. The easternmost longitude, related to the presence of the cloud on the flank of the volcano, was always lower than 238.5º E, i.e. not reaching the caldera (Figure 8f). The easternmost longitude of the head center occurred in the range Ls 270º-275º. Although measurements of the position of the cloud might be biased by the effect of parallax, given the estimated height of the cloud (see section 6), this effect is always within the range of error of our measurements.
VMC reveals a rich variety of morphologies, particularly in the head of the cloud, during the expansion phase of the AMEC from 6.5 to 8.5 LTST, when the cloud morphology is already well developed.

A scheme of the different features that we observe is presented in Figure 9a.
The earliest occurrences of the AMEC in the season show a small head and a tail with an approximately constant width, similar to the size of the head, and with no signs of turbulence (Figure 9b).  This morphology (Type I) was commonly observed before Ls 256º, and different observations differ mainly in the brightness of the tail. Following a gap with no suitable observations for this classification until Ls 266º (see Figure 2), different morphologies are observed at different LTST. In the early hours (6.9-7.6 LTST) the AMEC shows a Type II morphology (Figure 9c), with a bright textured head and smooth narrowing of the neck into a tail of decreasing width. Later in the day (7.3-8.4 LTST), we find Type III morphology, with a darker region separating the tail from a still bright head (Figure 9d). This morphology is often associated with a more undulating tail. Finally, prior to detachment (8.2-8.6 LTST), we often observe Type IV morphology, with a diminishing head and a broad tail that narrows away from Arsia Mons (Figure 9e).