Editing Galileo project (section)

==Venus encounter==
The encounter with [[Venus]] on February 9 was in view of the DSN's Canberra and [[Madrid Deep Space Communications Complex]]es.{{sfn|Mudgway|2001|p=306}} ''Galileo''{{'}}s closest approach to Venus came at 05:58:48 UTC on February 10, 1990, at a range of {{convert|16106|km|mi|abbr=on|sp=us}}.<ref name="PDS">{{cite web |title=PDS: Mission Information |publisher=NASA |url=https://pds.nasa.gov/ds-view/pds/viewMissionProfile.jsp?MISSION_NAME=GALILEO |access-date=November 9, 2020 |archive-date=July 17, 2017 |archive-url=https://web.archive.org/web/20170717152844/https://pds.nasa.gov/ds-view/pds/viewMissionProfile.jsp?MISSION_NAME=GALILEO |url-status=live }}</ref> Due to the [[Doppler effect]], the spacecraft's velocity relative to Earth could be computed by measuring the change in carrier frequency of the spacecraft's transmission compared to the nominal frequency.<ref>{{cite news |first=Morgan |last=Bettex |date=August 3, 2010 |title=Explained: The Doppler Effect |publisher=[[MIT News]] |url=https://news.mit.edu/2010/explained-doppler-0803 |access-date=April 15, 2024 |archive-date=September 28, 2023 |archive-url=https://web.archive.org/web/20230928014545/https://news.mit.edu/2010/explained-doppler-0803 |url-status=live }}</ref> Doppler data collected by the DSN allowed JPL to verify that the gravity-assist maneuver had been successful, and the spacecraft had obtained the expected {{convert|2.2|km/s|abbr=on|sp=us}} increase in speed. Unfortunately, three hours into the flyby, the tracking station at Goldstone had to be shut down due to high winds, and Doppler data was lost.{{sfn|Mudgway|2001|p=306}}

[[File:Galileo Venus global view.jpg|thumb|left|upright|Violet light image of Venus taken in February 1990 by ''Galileo''{{'s}} solid state imaging (SSI) system|alt=refer to caption]]
Because Venus was much closer to the Sun than the spacecraft had been designed to operate, great care was taken to avoid thermal damage. In particular, the [[X-band]] [[high gain antenna]] (HGA) was not deployed, but was kept folded up like an umbrella and pointed away from the Sun to keep it shaded and cool. This meant that the two small [[S-band]] low-gain antennae (LGAs) had to be used instead.{{sfn|Meltzer|2007|p=152}} They had a maximum bandwidth of 1,200 [[bits per second]] (bit/s) compared to the 134,000 bit/s expected from the HGA. As the spacecraft moved further from Earth, reception necessitated the use of the DSN's 70-meter dishes, to the detriment of other users, who had lower priority than ''Galileo''. Even so, the [[downlink]] [[telemetry]] rate fell to 40 bit/s within a few days of the Venus flyby, and by March it was down to just 10 bit/s.{{sfn|Mudgway|2001|p=306}}{{sfn|Johnson|Yeates|Young|Dunne|1991|p=1516}}

Venus had been the focus of many automated flybys, probes, balloons and landers, most recently the 1989 ''[[Magellan (spacecraft)|Magellan]]'' spacecraft, and ''Galileo'' had not been designed with Venus in mind. Nonetheless, there were useful observations that it could make, as it carried some instruments that had never flown on spacecraft to Venus, such as the near-infrared mapping spectrometer (NIMS).{{sfn|Johnson|Yeates|Young|Dunne|1991|p=1516}} Telescopic observations of Venus had revealed that there were certain parts of the infrared spectrum that the [[greenhouse gas]]es in the Venusian atmosphere did not block, making them transparent on these wavelengths. This permitted the NIMS to both view the clouds and obtain maps of the equatorial- and mid-latitudes of the night side of Venus with three to six times the resolution of Earth-based telescopes.{{sfn|Johnson|Yeates|Young|Dunne|1991|p=1517}} The ultraviolet spectrometer (UVS) was also deployed to observe the Venusian clouds and their motions.{{sfn|Johnson|Yeates|Young|Dunne|1991|p=1517}}{{sfn|Carlson et al.|1991|pp=1541–1544}}{{sfn|Belton et al.|1991|pp=1531–1536}}

Another set of observations was conducted using Galileo's energetic-particles detector (EPD) when ''Galileo'' moved through the [[bow shock]] caused by Venus's interaction with the [[solar wind]]. [[Earth's magnetic field]] causes the bow shock to occur at around {{convert|65000|km|mi|sp=us}} from its center, but Venus's weak magnetic field causes it to occur nearly on the surface, so the solar wind interacts with the atmosphere.{{sfn|Williams et al|1991|pp=1525–1528}}{{sfn|Meltzer|2007|pp=154–157}} A search for [[lightning]] on Venus was conducted using the [[plasma wave instrument|plasma-wave detector]], which noted nine bursts likely to have been caused by lightning, but efforts to capture an image of lightning with the solid-state imaging system (SSI) were unsuccessful.{{sfn|Belton et al.|1991|pp=1531–1536}}
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