Passing visitors: every gravity-assist flyby of Venus

For a spacecraft heading in toward the Sun, or out toward Jupiter and Saturn, Venus is a lever that costs no fuel. Between February 1974 and August 2025, spacecraft whose destinations lay elsewhere made 22 passes of the planet: one by Mariner 10, two by the Soviet Vega carriers, one by Galileo, two by Cassini, two by MESSENGER, seven by Parker Solar Probe, two by BepiColombo, four by Solar Orbiter and one by JUICE (azmth's count). Four Soviet landing missions added relay passes by their carriers, and two small Japanese craft drifted by in 2010.

A gravity assist borrows some of a planet's motion around the Sun. A spacecraft passing behind Venus leaves with more speed around the Sun, one passing in front leaves with less, and one crossing high over a pole has its orbital plane tilted. Parker Solar Probe's project scientist at the Johns Hopkins Applied Physics Laboratory (APL), Nour Raouafi, put its purpose plainly: flying by Venus slows the spacecraft so that it can dive closer to the Sun (NASA, 2021); Solar Orbiter used its early passes to shrink its orbit and uses the later ones to climb out of the plane of the planets (ESA). The price is precision: for the passes of August 2021, ESA says the approach paths were accurate to within a few kilometres at 187.7 million km from Earth.

Mariner 10 opened the list on 5 February 1974. NSSDCA records a closest range of 5,768 km at 17:01 UT and describes it as the first spacecraft to use the gravitational pull of one planet to reach another; Asif Siddiqi's NASA chronicle Beyond Earth calls it the first to use a gravity assist to change its interplanetary trajectory. The pass bent its path in toward Mercury, which it then flew past three times, and NSSDCA also credits it with the first close-up images of Venus.

The Soviet landers of 1978 and 1982 arrived on carriers that never stopped. NPO Lavochkin, their builder, calls the design a 'flyby and landing scheme' and each carrier an 'orbital craft', although none of them orbited anything but the Sun. Two days out, each carrier released its lander, swerved onto a miss trajectory and relayed the lander's signals as it passed; the design figure for the 1978 pair was 35,000 km. The Venera 11 and 12 carriers passed at 34,370 km on 25 December 1978 and about 34,000 km on 21 December, relaying 95 and 110 minutes from the surface; Siddiqi gives 35,000 km for both. For Venera 13 and 14 Siddiqi gives 36,000 km for each carrier. Lavochkin differs for Venera 14: after the lander separated on 3 March 1982 the divert burn gave 171.4 m/s instead of 227.8 m/s, and the carrier passed 26,050 km from Venus, which Lavochkin says was 10,000 km closer than needed to receive all the lander's data. Siddiqi reports the same shortfall and a pass much closer than planned, but at 36,000 km. Lavochkin's figure plus its 10,000 km comes to about 36,000 km; no source found explains the difference, so both stand. The guaranteed relay window shrank to 17 minutes after landing (Lavochkin).

Carriers also served as test beds. By 1980, Lavochkin writes, the next expedition (1984) was to go to Venus and then Halley's Comet, and the Venera 13 carrier was picked to rehearse the course corrections: after its pass it fired its engine on 10 June 1982 (192 m/s) to imitate aiming at a comet encounter, and again on 14 October (69.08 m/s), after which no propellant remained for the third burn in the plan. Siddiqi gives the same dates and adds a trajectory change by the Venera 14 carrier on 14 November 1982. Earlier, on 7 February 1979, the Venera 11 carrier had burned about 350 m/s (Siddiqi) for the Soviet and French Signe-2MZ1 gamma-ray burst experiment.

Halley's turn came in June 1985. Having released their landers and balloons, the Vega 1 and 2 carriers passed Venus on 11 and 15 June and swung toward Halley. Siddiqi gives 39,000 km for Vega 1 and no figure for Vega 2. The 1986 yearbook of the Great Soviet Encyclopedia, as reproduced in the Epizody kosmonavtiki archive, gives 39,000 km and 24,500 km from the surface for the two carriers, the only Soviet-era source found for the Vega 2 number. Lavochkin records corrections on 25 and 29 June 1985 that set the carriers on course for the comet, which they passed in March 1986.

Galileo, bound for Jupiter on a route that needed one pass of Venus and two of Earth, came by on 10 February 1990. JPL announced closest approach at one minute before 1 a.m. Eastern time (05:59 UTC), about 10,000 miles above the surface and 41 degrees south of the equator. Siddiqi gives 05:58:48 UT and 16,106 km, and the JPL Horizons trajectory gives 16,123 km above a sphere of 6,051.8 km. Venus added almost 5,000 mph to Galileo's speed, JPL said. Results published in Science in September 1991 included night-side maps from the Near Infrared Mapping Spectrometer showing opacity variations in the lower clouds near 50 km, plasma waves recorded near the bow shock and nine radio bursts between 100 kHz and 5.6 MHz, for which, Gurnett and colleagues wrote, lightning is the only known source.

Cassini, bound for Saturn with ESA's Huygens probe aboard, needed two passes. The first, at 13:44:41 UTC on 26 April 1998 by the Horizons trajectory (NASA's timeline says 25 April), came within about 284 km of the surface and added about 7 km/s (NASA). The second, on 24 June 1999 at 20:29:55 UTC, passed 602.6 km up, two seconds earlier and four kilometres higher than targeted, according to the project's weekly report. For the second pass several orbiter instruments were briefly switched on while Huygens stayed off (ESA). Both times the radio and plasma wave instrument listened for the high-frequency signals of terrestrial lightning and heard none, though it heard Earth's lightning easily on the Earth flyby of 18 August 1999. Gurnett's team concluded in Nature (2001) that any Venus lightning is either extremely rare or very different from Earth's. Set beside Galileo's bursts, the question remains open; see Atmosphere of Venus.

MESSENGER, bound for Mercury, used its two passes in opposite ways. On 24 October 2006 it passed 2,987 km above Venus at 08:34 UTC with the Sun lying between the spacecraft and Earth, and its principal investigator, Sean Solomon, said the team was not making any scientific observations, saving them for the next pass. On 5 June 2007 it returned at 338 km (23:08:19 UTC) with all seven instruments running as a rehearsal for Mercury. APL gives the effective velocity change as 5.523 km/s for the first pass and 6.937 km/s for the second. ESA's Venus Express was in orbit at the time, and APL's Ralph McNutt described the joint campaign as the first opportunity to measure interplanetary conditions and conditions at Venus simultaneously.

Two passengers of 2010 belong in the record, though neither sought a gravity assist. JAXA's solar sail IKAROS and the student-built Shin'en (UNITEC-1) left Earth with Akatsuki on 20 May 2010. The IKAROS team reported a pass about 80,800 km from Venus at 16:39 Japan time on 8 December (07:39 UTC). Shin'en's last communication came on 21 May 2010, with a beacon tracked until 31 May, and Siddiqi says only that the inert craft flew past sometime in December 2010.

Parker Solar Probe left Earth on 12 August 2018 and was at Venus 52 days later, on 3 October. Seven flybys between 2018 and 2024 shrank its orbit until perihelion reached about 6.1 million km from the Sun's surface (APL). NASA gave the distances at the time as about 1,500 miles (3 October 2018), about 1,870 miles (26 December 2019), 833 km (11 July 2020), 2,385 km (20 February 2021, a day-before figure that Horizons matches) and 3,814 km (16 October 2021); for the sixth pass, on 21 August 2023, the Horizons trajectory gives 4,006 km. The seventh, on 6 November 2024 at 18:43 UTC, was the closest. NASA put the aim point at about 240 miles (380 km) and APL says the craft flew precisely through it; Horizons gives 376 km, and APL's release converts the same 240 miles to about 387 km.

APL says Parker's early plans included no planetary science, but on 11 July 2020 the team turned WISPR, a camera built to image the solar wind, toward Venus in the hope of tracking the clouds. It saw through them: the night-side surface, at about 460 degrees C, glows faintly at the red edge of the visible spectrum, and WISPR's 470 to 800 nm band caught that glow, with the cooler highland Aphrodite Terra showing as a dark patch. The February 2021 pass lined up to image the whole night side, and Brian Wood's analysis appeared in Geophysical Research Letters on 9 February 2022. NASA calls these the first visible-light images of the surface taken from space; the first pictures from the ground came from the Venera 9 lander in 1975. The same July 2020 pass skimmed the upper atmosphere, where the FIELDS instrument recorded a natural radio emission for seven minutes. Glyn Collinson's team used it to measure the ionosphere, which had last been sampled directly by Pioneer Venus Orbiter in 1992, and found it much thinner near solar minimum.

BepiColombo, the European and Japanese mission to Mercury, passed Venus as a stack of two orbiters on a transfer module: ESA's Mercury Planetary Orbiter and JAXA's Mio. Its first Venus pass, on 15 October 2020 at 03:58:31 UTC, came 10,720.5 km above the surface by ESA's figure and 10,721.6 km by JAXA's, and slowed the stack by about 3.25 km/s. Most in situ instruments ran, with the MERTIS and PHEBUS spectrometers. JAXA coordinated the pass with Akatsuki, then in orbit around Venus, and with the Hisaki ultraviolet telescope in Earth orbit, and described the result as the first simultaneous planetary observation by three Japanese spacecraft missions. With the phosphine claim of September 2020 in the news, JAXA's Institute of Space and Astronautical Science (ISAS) noted that MERTIS covered wavelengths where phosphine absorbs; see Life on Venus.

August 2021 brought two visitors in 33 hours. Solar Orbiter passed 7,995 km from Venus at 04:42 UTC on 9 August, on the morning side; BepiColombo followed at 13:51:54 UTC on 10 August, only 552 km up, approaching over the night side. Neither could take high-resolution images with its science cameras, ESA said, but Solar Orbiter's SoloHI imager watched the planet in the days before and BepiColombo's monitoring cameras took black-and-white frames through closest approach. Each craft served as the other's solar wind monitor: BepiColombo sat upstream during Solar Orbiter's pass (ESA), and Solar Orbiter, between Venus and the Sun, did the same for BepiColombo's (ISAS). A team including ISAS reported in Nature Communications on 15 December 2022 that, at solar minimum, the solar wind was held off higher than models predicted, suggesting it does not inject energy straight into the ionosphere. Mio's Mass Spectrum Analyzer also caught cold oxygen and carbon ions about six Venus radii out in the flank of the induced magnetosphere, a region never sampled before, according to Hadid and colleagues in Nature Astronomy (12 April 2024).

Solar Orbiter, run by ESA with NASA, flies an orbit in resonance with Venus so that it comes back to the planet every few circuits of the Sun. Its first pass, on 27 December 2020 at 12:39 UTC, was about 7,500 km from the cloud tops. No images were possible because the spacecraft must keep facing the Sun, ESA explained, so only the magnetometer, the radio and plasma wave instrument and some particle sensors recorded. The third, on 4 September 2022 at 01:26 UTC, came 12,500 km from the planet's centre, shortly after a coronal mass ejection launched from the Sun on 30 August had swept over both the spacecraft and the planet (ESA). The fourth, on 18 February 2025, came within 379 km at 21:48 CET (20:48 UTC) and tilted the orbit from about 7.7 to about 17 degrees (angles that ESA's graphic and the Horizons notes measure from the Sun's equator), the step that gave ESA its first clear views of the Sun's south pole in June 2025.

ESA's Jupiter Icy Moons Explorer, JUICE, made its only Venus pass on 31 August 2025 at 07:28 CEST (05:28 UTC), after a communications anomaly in July had been cleared. SSC Space, whose engineers helped plan the flyby within ESA's control team, gives the distance as 5,088 km, which the Horizons trajectory matches. The spacecraft is built for the cold of the Jupiter system, so near Venus it kept its high-gain antenna pointed at the Sun as a heat shield, and SSC says no science observations were made. The JUICE data sheet in JPL Horizons (revised 27 September 2026) still gives a last Earth flyby in January 2029 and arrival at Jupiter in July 2031, and lists no further Venus pass.

The next spacecraft due at Venus is Solar Orbiter again, on 24 December 2026. ESA's flyby table says the pass will raise the inclination to 24 degrees and mark the start of the high-latitude mission. JPL's Horizons system, carrying ESA's trajectory fitted to tracking up to 17 September 2026, predicts closest approach at 22:57:48 UTC, about 948 km above the surface, at 20.8 km/s (queried 4 November 2026). Three more are scheduled in ESA's table, which adds that dates are subject to change: 18 March 2028, 10 June 2029 and 2 September 2030. ESA's planned trajectory in Horizons puts the first two at exactly 350.0 km, round figures that look like planning aim points, and the last at 02:58 UTC on 3 September 2030, 2,618 km up, one calendar day after ESA's date. No other past visitor is due back: APL called Parker's 2024 pass its final one, and the Horizons trajectories of Parker (queried to 2030), BepiColombo (to April 2027) and JUICE (to July 2031) show no later approach within 1.5 million km.

An Emirati spacecraft is the next new flyby visitor on the calendar. The mission was announced in 2021 as the 'Emirates mission to explore Venus and the asteroid belt', and the government portal still says it will explore the planet Venus. When the UAE Space Agency set out the full plan on 29 May 2023, the spacecraft was named MBR Explorer and Venus had become one of three gravity assists, with Earth and Mars, on a five-billion-kilometre tour of seven asteroids ending at (269) Justitia. An H3 launch was contracted from Mitsubishi Heavy Industries on 9 October 2024; Al Bayan (17 February 2026), The National (27 April 2026, with assembly and testing under way) and the news agency WAM (4 October 2026) give the first quarter of 2028, and Khaleej Times (4 September 2026) says March 2028. The National dated the Venus pass to July 2028 in its report of the 2023 briefing; no 2026 or Arabic source found restates the month or gives an altitude, so July 2028 remains the 2023 plan.

A 2020 study by NSSC and European partners for a Chinese mission to the Jupiter system, presented under the name Gan De, drew a Venus flyby on 11 April 2030 at 12,716 km after a launch on 2 October 2029. China's Jupiter mission is now Tianwen-4, and no official source found says whether it keeps that route: in April 2026 Guan Feng, director of the China Lunar Exploration and Space Center, said only that Tianwen-4 is within the plan and will explore Jupiter and its moons, with no date. NASA's DAVINCI, with a December 2031 launch baseline (its team now works toward December 2030), plans flybys before its probe descends, but it is bound for Venus itself. Russia's Interhelioprobe, a solar probe that was to use repeated Venus gravity assists, grew out of the Russian and German Interhelios project of the late 1990s and never flew. In February 2016 the IKI director Lev Zelenyi said budget cuts had pushed its launch beyond 2025; in February 2019 Vladimir Kuznetsov, director of IZMIRAN, said funding for 2019 to 2021 had been cut so sharply that the manufacturing contract would be re-let and the formal 2026 date would not hold. No later status was found.

Planetary geometry sets every launch and flyby date. Earth and Venus return to the same relative positions every 583.92 days, and each return opens a launch window for a direct flight (Don P. Mitchell's table of Venus missions). In 1978 two American and two Soviet launches put ten separate craft at Venus between 4 and 25 December: the Pioneer Venus orbiter, the multiprobe bus and its four probes, and two landers with their two flyby carriers. Mitchell marks the Type I windows of 1977, 1980, 1986 and 1988 as unused; Siddiqi says the Challenger accident delayed Magellan by at least a year, and it left on 4 May 1989 on a path one and a half times around the Sun. Mitchell lists 1991, 1993, 1994 and 1996 as unused too.

Two long gaps frame the gravity-assist era. After Magellan's launch on 4 May 1989, no mission whose destination was Venus left Earth until Venus Express on 9 November 2005, a gap of 6,033 days counted by calendar date, with only Galileo and Cassini passing by in between. Since Akatsuki and its passengers left on 20 May 2010, no mission to Venus has been launched. On 4 November 2026 that gap stood at 6,012 days, and it equals the earlier one on 25 November 2026. The next launch aimed at Venus on the schedule is India's Venus Orbiter Mission, targeted for March 2028 by the Indian government (June 2026); the Rocket Lab and MIT probe of the Venus Life Finder effort has no date and awaits Rocket Lab's unflown Neutron rocket. Announced plans for VERITAS, DAVINCI, EnVision and Venera-D all point to the 2030s; their own pages carry their current dates.