JuanCastillo29/space-mission-intelligence-data huggingface dataset:
The quality of the PRIDE science products derived from VLBI data relies on the observations of a nearby phase calibrator source [48], which is often a quasar with a well-defined position in the ICRF. Both spacecraft and calibrators must be viewed through the same patch of the sky to remove atmospheric interference due to the ionosphere and the troposphere, and instrumental phase errors. If a calibrator is too far from the target, variations in the atmosphere make it impossible to correct these effects. Usually, if the calibrator is within ∼2◦[43] of the target, calibration can be performed. However, the telescopes must be steered back and forth between the target and the calibrator on a frequent basis, a procedure known as nodding. In cases where suitable reference sources are available and with proper planning and scheduling, calibration can be improved using in-beam phase referencing. This technique involves observing the reference source within the same telescope’s primary beam as the target source, removing the need for nodding and improving data quality. The accuracy and precision of the resulting VLBI data point of JUICE will depend on the quality and closeness of the phase reference source. In case suitable phasereference sources close to JUICE during a period of specific scientific interest are not available, a dedicated observation campaign can be conducted specifically to densify the catalogue of suitable reference sources in the patch of the sky of interest. However, such a campaign must be executed separately from and well in advance of the spacecraft VLBI observations and should only be done if the ultimate science case for doing so is sound. An example of such a preparatory VLBI experiment is described in Section 4.3 for the case of the JUICE Venus flyby. The PRIDE technique can also be applied to simultaneously receive the signals from two or more transmitting spacecraft, which can be used to create multi-spacecraft in-beam VLBI observations, providing the relative angular position of the two spacecraft in ICRF to be determined with an accuracy similar to regular VLBI observables. In the context of JUICE, this will provide unique opportunities for conducting concurrent in-beam PRIDE observations of JUICE and NASA’s Europa Clipper, with potentially significant advantages in creating a consistent and coupled dynamical solution for the Galilean satellites from the data sets of the two missions [46].

Using the ExoMars Trace Gas Orbiter [49] and Mars Express [50], a preliminary study of such a dual-spacecraft PRIDE experiment was carried out by [51] in Mars orbit. A comparison of the propagation effects on simultaneous tracking of Mars Express and Tianwen-1 was reported by [52]. Provided that the opportunity arises, a future PRIDE observation campaign during the cruise phase will be planned where a second spacecraft is visible within ∼2◦of JUICE in preparation for the operations in the Jovian system.
We present an overview of the operations and engineering interface for Planetary Radio Interferometry and Doppler Experiment (PRIDE) radio astronomy observations as a scientific component of the ESA’s Jupiter Icy Moons Explorer (JUICE) mission, as well as other prospective planetary and space science missions. The article discusses advanced scheduling and planning methods that make it possible to create observing schedules for observations of specific spacecraft in concurrence with observations of natural radio sources. In order to put this into practice and find suitable natural background calibrator sources for PRIDE of JUICE mission, we developed planning and scheduling software. The conventional scheduling software for natural celestial radio sources is not set up to include spacecraft as observation targets in the necessary control files. Therefore, difficulties already arise during observation planning. We report on the development of new and the adaptation of existing routines used in astrophysical and geodetic VLBI for satellite scheduling and planning. The analysis of the PRIDE science observations led to improved observational planning, and the mission’s scheduling methodologies were studied using a systems engineering approach. In addition, we highlighted the new procedures, like finding charts for selecting calibrator radio sources over a range of frequency bands and the outcomes of those strategies for science operation planning. A simulation of the flyby of Venus during the cruise phase of the JUICE spacecraft, based on the Tudat software, is also presented, resulting in a promising opportunity to test PRIDE techniques and evaluate the improvements that PRIDE observables can make to natural bodies’ ephemerides. The first Ka-band (32 GHz) observations of the ESA’s BepiColombo by a radio telescope in the VLBI network, which employs a similar radio communications system as JUICE, were also demonstrated as a test case. The primary objective of these activities is to serve as a practice run for the upcoming operational PRIDE JUICE operations. We showcase the capabilities of the planning and scheduling software for other space missions.
Keywords: Interferometry, VLBI, Planetary missions, Space science missions, Radio astronomy, JUICE, PRIDE
and implementation

On April 14 2023, JUICE was launched from the Guiana Space Centre in Kourou, French Guiana, using the Ariane 5 ECA (Evolved Cryogenic, model A) launch vehicle The communications subsystem of the spacecraft is composed of a redundant set of Deep Space Transponders (DSTs)

[Figure: Fig. 2 Global distribution of VLBI radio telescopes (shown by yellow dots). Most of the shown telescopes can operate at X-band (8.4 GHz), some at Ka-band (32 GHz). Several of the latter can do simultaneous X/Ka observations. The map reflects the status as of March 2024. During the operational lifetime of the JUICE mission, this map might change as more VLBI-compatible radio telescopes come online. Credit: the background map is a satellite image composite provided by Blue Marble Next Generation, courtesy of NASA Visible Earth (https://visibleearth.nasa.gov).]

[38]. The mission is comprised of three phases, namely, a cruise phase, a Jupiter tour beginning in July 2031 with the Jupiter Orbit Insertion (JOI), and a Ganymede phase beginning in December 2034 with the Ganymede Orbit Insertion (GOI), and ending nominally in September 2035. As per the most recent mission’s Consolidated Report on Mission Analysis (CReMA) 5.0b23 [39], JUICE will conduct numerous flyby studies of Ganymede, Callisto, and Europa before entering the polar orbit around Ganymede in 2034. The cruise phase, which will span for roughly 8 years prior to the JOI, will feature a flyby of the Moon and Earth in August 2024, a flyby of Venus in August 2025, and two Earth flybys in September 2026 and January 2029, respectively. As a scientific possibility, a flyby of one or more asteroids has been investigated [40]. We summarize the JUICE radio systems, the signal from which PRIDE uses to generate its observables, in Section 2.1, followed by a brief overview of the PRIDE– JUICE science objectives and operations in Section 2.2.
that use the X-band for the uplink and the X- and Ka-band for the downlink. The science payload also includes the KaT transponder, which is a part of the onboard radio science instrument 3GM [Gravity and Geophysics of Jupiter and the Galilean Moons; 41]. This transponder allows a Ka-band up- and downlink to be used for the generation of high-accuracy radio science Doppler and range data. The spacecraft antennas consist of a stationary high-gain antenna (HGA) (dual-band X and Ka), a steerable medium-gain antenna (MGA) (dual-band X and Observation Block evaluation and data telescopes to processing Ka), and two stationary X-band low-gain antennas (LGA).
[Figure: Fig. 3 PRIDE VLBI observation run activities and data processing. The main steps involve the scheduling of observation blocks, the preparation of .vex files, and the collection of calibration and baseband data for each telescope. The final visibility data released to the PI is bundled with calibration data. For near-field or far-field VLBI, signal processing can include delay models as well as optional processing like pulsar processing, space VLBI antenna support, multiple phase centers for widefield VLBI, spectral windowing, or customized channelization. Data review and archiving to EVN or Planetary Data System (PDS) Standard is the final step.]

During the cruise, X-band uplink and downlink are the default settings. The JUICE mission is operated by the ESA ground segment, consisting of the Mission Operations Centre (MOC) and the Science Operations Centre (SOC). MOC is in charge of ground segment development and spacecraft operations, while SOC is in charge of arranging, preparing, and sending the science operation requests to the MOC and coordinating the distribution of the data obtained from the MOC. The PRIDE ground segment can conduct observations whenever the spacecraft emits a radio signal for communication or radio science. Since the spacecraft already has onboard radio instrumentation required for PRIDE installed for other purposes (like navigation and communication), PRIDE does not affect the mission’s payload mass budget.
Most of the science objectives of PRIDE are addressed by exploiting the natural synergy between PRIDE [8] and 3GM [41]. 3GM will provide highly precise range and Doppler measurements, following procedures developed for the Mercury Orbiter Radio science Experiment (MORE) experiment on BepiColombo [which is very similar to 3GM; 42]. PRIDE will provide Doppler estimates at each receiving radio telescope in addition to the Doppler data obtained by 3GM at a dedicated tracking station. PRIDE can in principle operate with any radio signal coming from JUICE, but the typical operating mode for tracking will use the coherent downlink, from an uplink of an ESTRACK station.

[Figure: Fig. 4 Interplanetary cruise phase and summary of transfer options for launch in 2023. Colour-code is used: green for Venus Gravity Assist (VGA), blue for the Earth Gravity Assist (EGA), orange for the Lunar-Earth Gravity Assist (LEGA) [39]. Note that the JUICE launch occurred a little more than a week earlier than the baseline plan in this figure, which does not impact the general trajectory planning shown here.]

The noise parameters of PRIDE measurements are enhanced if the JUICE radio signal is not only transponded at X-band, but at Ka-band as well (when available, from a combined X- and Ka-band uplink), as this permits calibration of noise due to charged particles. This dual-frequency operation is facilitated by the 3GM Kaband transponder (KaT). The operational advantage of PRIDE is in its ability to use multiple Earth-based receiving antennas thus having higher chance to pick up the best weather, ionosphere conditions as well as higher elevation of JUICE over local horizon (see an example of this advantage in VEX radio occultation experiments described in [43]). For further discussion on the role of PRIDE in the overall JUICE radio science experiments see [6]. Furthermore and most importantly for the topics discussed here, PRIDE will provide VLBI data for the lateral spacecraft position in the International Celestial Reference Frame [ICRF; 44]. PRIDE VLBI measurements are anticipated to improve the calculation of Jupiter’s normal positions (out-of-plane direction) and of the Galilean satellites. particularly Callisto [25, 45]. In addition, the PRIDE VLBI data will be valuable as an independent validation of ephemeris solutions and, as such, will be of great value in developing a fully coupled dynamical solution of the JUICE spacecraft, the Galilean satellites, and Jupiter itself [26, 46]. A complete overview of the synergies with other instruments is discussed by [6]. In addition to science data products extracted from determining spacecraft dynamics, PRIDE will be used to perform radio occultation experiments on the Galilean satellites and Jupiter as probes for the atmospheres of these bodies, as done in the past for Venus using PRIDE [43]. The very large collecting area of the radio telescopes involved in PRIDE, compared to regular single tracking station observations, as well as the more diverse observing geometry and local meteorology conditions facilitated by PRIDE’s global nature, will allow facilitating a better quality occultation measurements.
, 46]. A complete overview of the synergies with other instruments is discussed by [6]. In addition to science data products extracted from determining spacecraft dynamics, PRIDE will be used to perform radio occultation experiments on the Galilean satellites and Jupiter as probes for the atmospheres of these bodies, as done in the past for Venus using PRIDE [43]. The very large collecting area of the radio telescopes involved in PRIDE, compared to regular single tracking station observations, as well as the more diverse observing geometry and local meteorology conditions facilitated by PRIDE’s global nature, will allow facilitating a better quality occultation measurements.

Using multiple stations for PRIDE signal detection could reduce propagation errors due to the Earth’s atmosphere, improve spatial resolution and geometric accuracy, improve overall signal strength, and minimize noise. This increases the signal-to-noise ratio (SNR), which ensures higher-quality observations and is essential in detecting faint signals from spacecraft during occultations. The study by [43] demonstrated that occultations with Venus Express (VEX), utilizing PRIDE stations, achieve deeper penetration into the Venusian atmosphere compared to those performed with the dedicated Deep Space Network (DSN) and ESTRACK facilities. PRIDE will also be useful in studying the interplanetary medium, as demonstrated in [47]. The operations of the ground segment of PRIDE solely depend on the ability and availability of ground-based radio telescopes to conduct PRIDE observations. The latter is defined by the telescope–spacecraft geometry configuration, the mission radio-link schedule, and the type of radio signal (carrier/modulated spectrum). In a nutshell, the PRIDE implementation solely uses existing technologies as a piggyback application during any interaction between the major Earth-based assets of PRIDE and the JUICE mission. However, compared to regular radio science for planetary spacecraft, planning PRIDE observations has the added complexity that the quality of all science products derived from the VLBI data will depend on the quality of the available phase calibrator(s) and the (time-variable) visible network of stations during the observation, which all have an influence on the quality of the angular position of JUICE as produced by PRIDE. These complexities are not present for ‘regular’ radio science observations, and their impact is therefore not studied in much detail. The desire to automate and (where possible) optimize for these added complications in large part motivates the need for the work presented here.

[Table: Table 2 Cruise phase flyby summary according to [39].]

| Flybys | Time UTC Altitude [km] |
| --- | --- |
| Moon FB Earth FB Venus FB Earth FB Earth FB | 2024-08-19T19:34:20 750.11 2024-08-20T20:15:27 6402.95 2025-08-31T06:18:12 5081.73 2026-09-28T11:53:56 8641.88 2029-01-17T18:27:20 4643.97 |
An overview of PRIDE experiment planning and scheduling methods for the various mission phases is presented in this section, as well as an overview of their application during the cruise phase. Note that, in the present context, the term ‘planning’ is used for the general overall procedure of deciding when to do the observations, while | Description Experiment Type | Observations during communication/downlink sessions Nominal and/or Delta DOR (Differential One-way Range)

sessions outside of flybys Observations close to the Venus fl yby. Acquisition of VLBI Nominal data for improvement of solar system ephemerides Acquisition of occultation proflies at Venus and/or Moon (dur- Occultations ing Lunar flyby) (for science and/or tests) Acquisition of training data sets for operations in the Jovian Test and training system (‘regular’ mode, ‘in-beam with calibrator’ mode, ‘in- beam with second spacecraft’ mode) |

| --- | --- |
| Experiment Code | PRIDE-EXP1 PRIDE-EXP2 PRIDE-EXP3 PRIDE-EXP4 |

[Table: Table 3 The types of PRIDE observations during the cruise phase.Each experiment’s duration is ≥2 h]

.
The overall and nominal activities of the PRIDE observation run are shown in Fig. 3. It depicts how PRIDE observations are planned, including which radio telescopes will observe which spacecraft at what time. The observation is planned using custom-built planning software. The scheduling is accomplished by VLBI specialized software called SCHED or, more recently, pySCHED1. The input for the scheduling software is created from the results of the developed planning tool and ad hoc scripts2 for calculating spacecraft coordinates and adding a variety of desired scheduling parameters. The accurate computation of source visibilities, taking into account each antenna’s sensitivity, antenna mounting, slewing rates, and source strength are essential components of a scheduling tool. The outputs are standard-format schedules that each participating radio telescope uses to acquire its data. The antenna steering, signal chains, and sampler (digitizer) configuration, as well as the recording mode, are all contained in the station-specific schedule file, which is also defined in the process of scheduling. A proper time schedule, including uplink and downlink sessions, UT range, and the predicted position of a spacecraft at different epochs, is required to observe spacecraft signals with VLBI radio telescopes. These inputs are anticipated from the SOC and/or MOC well in advance and should be prepared before an observation, according to the tracking session information and CReMA documentation [39]. After the observation planning and scheduling, each of the participating ground stations sends its raw data to JIVE in the prescribed format. The open-loop VLBI/Doppler signal processing methods described in [9, 11] are used to analyze this time domain received data. Finally, the mission’s post-processing and archiving will be carried out in accordance with the Planetary Data System (PDS) archiving guidelines.
As described in Section 3.1, the initial step of the PRIDE implementation process involves identifying science opportunities at distinct mission phases in accordance with the mission’s overall science operations plan. In this section, we present the tools we have developed to support the planning and scheduling and provide illustrative results for past and upcoming experiments. The specifics of the custom-developed observational planning tool, primarily the identification of potential phase referencing calibrators near the celestial position of the spacecraft at a given epoch, is discussed in Section 4.1. Section 4.2 describes the application of the PRIDE observation planning and scheduling tool to the BepiColombo mission, which represented the PRIDE team’s initial acquisition of a spacecraft signal at Ka-band and demonstrated PRIDE’s conceptual feasibility in Ka-band. The planning of a preparatory VLBI experiment to characterise calibrator sources and to look for potentially suitable in-beam phasereference calibrators prior to the JUICE Venus flyby in 2025 is presented in Section 4.3. Finally, Section 4.4 presents the results of numerical simulations to highlight the importance of effective planning and scheduling and proper selection of different phase calibrators for PRIDE–JUICE during its first end-to-end test for the acquisition of VLBI data and improving ephemerides:

[Figure: Fig. 7 PRIDE observational planning chart for the cruise phase of the JUICE mission (CReMA 5.0) for the time period of 2025.01.01 to 2025.12.31. The middle panel shows the whole sky in the Mollweide projection populated with the RFC celestial sources (blue dots). The upper and two lower panels (framed in orange color) show zoomed-in finding charts for periods of one day and one month, respectively. Red dots indicate potential reference sources from the RFC [53] that are within 1◦of the JUICE spacecraft’s ephemeris. Blue lines indicate the JUICE celestial track as per CReMA 5.0. The shadowed area indicates the celestial positions within 1◦from the JUICE celestial track. In general, the calibrators are distributed uniformly along the JUICE spacecraft sky track.]

[Figure: Fig. 8 BepiColombo-PRIDE planning chart for January 1, 2022, to December 31, 2022. The upper panel shows the whole sky in the Mollweide projection populated with the RFC celestial sources (blue dots). The lower panel (framed in orange color) shows a zoomed-in finding chart for a period of one day. Red dots indicate potential reference sources from the RFC that are within 1◦of the BepiColombo spacecraft’s ephemeris. Blue lines indicate the BepiColombo celestial track, along with any probable reference sources.]

the Venus flyby (see Sections 3.3 and 4.3).
For PRIDE experiments with past planetary missions such as Mars Express and Venus Express, numerous manual actions were required to meticulously prepare the necessary observation plans, scheduling, and related interchange files. The issue in the case of the VLBI spacecraft observations was that the widely used geodetic scheduling systems did not normally support spacecraft as radio sources. In addition, because spacecraft missions are dynamic and require scheduling and coordination not only between the receiving telescopes but also between the transmitting station and spacecraft, the procedure of scheduling observations presents a number of additional difficulties. Spacecraft orbit and visibility, spacecraft operational constraints, flexibility for real-time adjustments, coordination of multiple observing modes, distribution of baseline lengths, and data prioritization are the main challenges when scheduling VLBI observations of spacecraft. To address these challenges and streamline the process as much as possible, we have created a specialized spacecraft observation planning and scheduling module. It makes it easy and practical to create realistic satellite observation plans for upcoming experiments with only the bare minimum of required input from users. Figure 5 depicts the PRIDE planning and scheduling program’s software stack.
• L0 (Input): This module contains all the experiment’s input, such as the start and stop dates, reference frame, reference catalogue, SPICE metakernel, the time step, etc.
• L1: with this module, potential reference sources are identified and classified based on the spacecraft trajectory. This module calculates the JUICE trajectory using Spicepy [55] (a Python wrapper for the SPICE toolkit [56]) and extracts the VLBI RFC coordinates using Astropy [57].
• L2 (Output): visualization in the form of a finding chart in Mollweide projection and zoom-in charts for a specific event are produced for the specific experiment of interest.
The Radio Fundamental Catalogue (RFC) by [53] is the most complete catalogue of compact radio sources currently available for potential calibrators’ searches. The RFC was created by analysis of all available VLBI data produced under absolute astrometry and geodesy programs as well as other VLBI studies to offer milliarcsecond-accurate locations, maps, and estimates of correlated flux densities for thousands of compact radio sources. It includes a total of 21,906 sources detected (Fig. 6) with VLBI between 1980 and 2023. Making a so-called finding chart (as in Fig. 7), which displays the target spacecraft’s (JUICE) coordinates as seen from Earth over a period of time, is the first step of the tool. For the purpose of observing weak objects or conducting astrometry studies, phase-referencing calibrator sources are required. These sources must be compact, with a strong signal on all baselines (above 0.3 Jy), ensuring accurate phase calibration. The availability of appropriate stations on the ground and knowledge of stable radio 50 Cd Ke Mp 40