more details.
VLBI Array Number of telescopes X-band Ka-band
European VLBI Network (EVN) 22 22 6 U.S. Very Long Baseline Array (VLBA) 10 10 10 Japanese VLBI Network (JVN) 9 9 – Chinese VLBI Network (CVN) >6 6 1 Korean VLBI Network (KVN) 3 – 3 East-Asia VLBI Network (EAVN) 15 3 – Australian Long Baseline Array (LBA) 5 5 2 University of Tasmania Array 5 5 –]

In a typical PRIDE session, a network of Earth-based radio telescopes observes the JUICE spacecraft in phase-referencing VLBI mode. PRIDE does not have any dedicated onboard instrumentation and relies on the mission’s radio communication systems. The main instrumental asset of PRIDE is the global network of VLBIequipped radio telescopes, data transfer and data processing facilities. For a particular PRIDE observing run, a combination of Earth-based radio telescopes can be composed of a large set of facilities distributed over the globe, as shown in Fig. 2 and listed in Table 1 as of March 2024. In most cases, the VLBI telescopes are built and operated in the interests of galactic and extragalactic astronomy, astrometry and geodesy, and are unrelated directly to the JUICE or any other space science mission. PRIDE uses these resources in an ad hoc regime. The telescopes involved in PRIDE observations receive the radio signal transmitted by spacecraft. In PRIDE–JUICE, the nominal observing mode is at the X-band (8.4 GHz), but observations at the Ka-band (32 GHz) are possible too.

The VLBI technique entered the domain of planetary science and exploration more than half a century ago – see a review of planetary and space science missions supported by VLBI in [6]. In most cases, VLBI observations of planetary probes were conducted as ad hoc complements, not a part of nominal science suites of the mission (e.g., VLBI tracking of the ESA’s Titan Huygens Probe [28, 29], and VLBA observations of the Cassini spacecraft [30]). In some relatively rare cases, VLBI tracking was included as a nominal component of the mission’s scientific operations. This was the case of the Venusian balloons of the VEGA mission and support to the Giotto Halley comet rendezvous [31–33]. The Chinese exploration programs of the Moon (Chang’e [34]) and Mars (Tianwen [35]) include VLBI tracking as a nominal state vector determination and navigation technique. The Japanese Lunar Probe SELENE [36] and Venusian solar sail IKAROS [37] also relied on VLBI support. However, in all these examples, VLBI tracking was exploited over a relatively short mission duration. The VLBI component of the JUICE mission implemented as PRIDE differs from the above predecessors in the operational duration: 8.5 years of the cruise phase and at least 3 years of the Jovian tour. It is also the first occasion of the inclusion of PRIDEVLBI as a nominal component in a mission to the outer Solar System. While the methodology of VLBI tracking of planetary missions has been developed and demonstrated by the PRIDE group over the past 20 years [see 6, and references therein], the higher load on VLBI operations as a nominal component of the JUICE mission required new approaches for planning and implementing a massive observing campaign using global VLBI networks. These ground-based VLBI operations should be properly integrated with the equally sophisticated but fundamentally different operational routines of the JUICE planetary mission. In this paper, we present this interface as well as our developments to prepare for the high operational load once in the Jovian system and give examples of consistent operational routines of the ground-based VLBI networks and the JUICE mission. The paper is organized as follows: the configuration of PRIDE and its interaction with JUICE, as well as the science requirements and how it works in conjunction with other instruments, are covered in Section 2. In Section 3, details on the experimental planning and scheduling methods are discussed. There, the various reasons why this will impact the data quality are described, and the various opportunities during the cruise phase where this impacts on the JUICE mission will be outlined. In Section 4, we present the specific tools that have been developed to automate planning and scheduling, show the application and results of these tools for the first PRIDE Ka-band observations of the BepiColombo spacecraft, and provide numerical simulations to quantify the potential impact that these tools could have on science return from PRIDE observations during the Venus flyby experiment. Finally, the concluding remarks and outlook are provided in Section 5.