Venera program

thumb|Position of Venera landing sites. Red points denote sites returning images from the surface, black central dots sites of surface sample analysis. Map based on mapping from [[Pioneer Venus Orbiter and Magellan.]]

The Venera program (, 'Venus') was a series of space probes developed by the Soviet Union between 1961 and 1984 to gather information about the planet Venus. A total of eighteen probes were sent, including two related Vega probes.

Thirteen probes successfully entered the Venusian atmosphere, including the two Venera-Halley probes. Ten of those successfully landed on the surface of the planet. Due to the extreme conditions, the probes could only survive for a short period on the surface, from 23 minutes to two hours.

The Venera program established a number of precedents in space exploration, among them being the first man-made devices to enter the atmosphere of another planet (Venera 3 on 1 March 1966), the first to make a soft landing on another planet (Venera 7 on 15 December 1970), the first to return images from another planet's surface (Venera 9 on 8 June 1975), the first to record sounds on another planet (Venera 13 on 30 October 1981), and the first to perform high-resolution radar mapping scans (Venera 15 on 2 June 1983). The intense pressures that led to the short lifespans of many of the probes was itself an important finding.

The Venera probes

Venera 1 and 2

thumb|upright|Full-scale model of the [[Venera 1 in the Memorial Museum of Cosmonautics]]

The first Soviet attempt at a flyby probe to Venus was launched on 4 February 1961, but failed to leave Earth orbit. In keeping with the Soviet policy at that time of not announcing details of failed missions, the launch was announced under the name Tyazhely Sputnik ("Heavy Satellite"). It is also known as Venera 1VA. As with some of the Soviet Union's other planetary probes, the later versions were launched in pairs, with a second vehicle launched soon after the first.

Venera 1 and Venera 2 were intended to fly past Venus without entering orbit. Venera 1 was launched on 12 February 1961. Telemetry on the probe failed seven days after launch. It is believed to have passed within of Venus and remains in heliocentric orbit. Venera 2 launched on 12 November 1965, but also suffered a telemetry failure after leaving Earth orbit. Several other failed attempts at Venus flyby probes were launched by the Soviet Union in the early 1960s, but were not announced as planetary missions at the time, and hence did not officially receive the "Venera" designation.

Venera 3 to 6

The Venera 3 to 6 probes were similar in construction. Weighing approximately one ton, and launched by the Molniya-type booster rocket, they included a cruise "bus" and a spherical atmospheric entry probe. The probes were optimised for atmospheric measurements, but not equipped with any special landing apparatus. Although it was hoped they would reach the surface still functioning, the first probes failed almost immediately, thereby disabling data transmission to Earth.

Venera 3 became the first human-made object to impact another planet's surface as it crash-landed on 1 March 1966. However, as the spacecraft's data probes had failed upon atmospheric penetration, no data from within the Venusian atmosphere were retrieved from the mission.

On 18 October 1967, Venera 4 became the first spacecraft to measure the atmosphere of another planet. This spacecraft first showed the major gas of Venus's atmosphere to be CO2. While the Soviet Union initially claimed the craft reached the surface intact, re-analysis, including atmospheric occultation data from the American Mariner 5 spacecraft that flew by Venus the day after its arrival, demonstrated that Venus's surface pressure was 75–100 atmospheres, much higher than Venera 4's 25 atm hull strength, and the claim was retracted.

Realizing the ships would be crushed before reaching the surface, the Soviets launched Venera 5 and Venera 6 as atmospheric probes. Designed to jettison nearly half their payload prior to entering the planet's atmosphere, these craft recorded 53 and 51 minutes of data, respectively, while slowly descending by parachute before their batteries failed. This represented a significant scientific accomplishment. It had become increasingly clear that Venus was unlikely to have liquid bodies of water but designs for the Soviet Venera probes still considered the possibility of a water landing as late as 1964.

Venera 7

thumb|Model of Venera 7 lander in the Cosmos Pavilion, [[VDNKh (Russia)|VDNKh]]

The Venera 7 probe, launched in August 1970, was the first one designed to survive Venus's surface conditions and to make a soft landing. Massively overbuilt to ensure survival, it had few experiments on board, and scientific output from the mission was further limited due to an internal switchboard failure that stuck in the "transmit temperature" position. Still, the control scientists succeeded in extrapolating the pressure (90 atm) from the temperature data with , which resulted from the first direct surface measurements. The Doppler measurements of the Venera 4 to 7 probes were the first evidence of the existence of zonal winds with high speeds of up to in the Venusian atmosphere (super rotation). Along with the pressure and temperature data acquired Venera 7 also measured atmospheric composition. When the system was switched to radio altimeter mode the antenna operated at an 8-centimeter wavelength band to send and receive signals off of the Venusian surface over a period of 0.67 milliseconds.

The results were a detailed map of the reflectivity distribution over the surface of the Venusian Northern Hemisphere. The linear distance measurements that were taken ranged from 91 to 182 kilometers. The twin Soviet spacecraft flew in near-polar elliptical orbits and succeeded in mapping the top half of the northern atmosphere (from the north pole to 30 degrees N latitude, about 115 million square kilometers or 71 million square miles) by the end of the main mission. An altimeter provided topographical data with a height resolution of 50 m (164 feet), and an East German instrument mapped surface temperature variations.

VeGa probes

The VeGa (Cyrillic: ВеГа) probes to Venus and comet 1/P Halley launched in 1984 also used this basic Venera design, including landers but also atmospheric balloons which relayed data for about two days. "VeGa" is a portmanteau of the words "Venera" (Venus in Russian) and "Gallei" (Halley in Russian).

Future

Venera-D

Venera-D is a proposed mission to Venus that would include a highly capable orbiter and a lander. From the standpoint of total mass delivered to Venus, the best launch opportunities occur in 2026 and 2031; however, as of March 2021, Venera-D is planned for launch no earlier than November 2029. Venera-D could incorporate some NASA components, including balloons, a subsatellite for plasma measurements, or a long-lived (24 hours) surface station on the lander.

Scientific findings

thumb|588x588px|center|First view of Venus's surface or any other planet other than Earth. The first clear panoramic image taken by Venera 9 lander. This image was sent back in the lander's 53-minute lifetime 22 October 1975. Although it was intended to be a 360-degree image, the second camera's lens cap did not open resulting in this 180-degree panorama.

There were many scientific findings from the data retrieved by the Venera probes making them pivotal in our understanding of Venus. The Venera probes provided direct data regarding Venus's surface and atmosphere while also providing important information on electronics lifetime under Venus's harsh conditions. Venera 4 was the first successful probe, and showed that CO2 is the main component in Venus's atmosphere. Venera 8 measured the K, U, and Th on the surface through gamma-ray analysis. By sending the first images of Venus's surface back to Earth the Venera missions provided scientists with the ability to relay the achievements with the public. Venera 13 provided the first color images and X-ray fluorescence data of the surface of the planet. After analyzing the radar images returned from Venera 15 and 16, it was concluded that the ridges and grooves on the surface of Venus were the result of tectonic deformations. This was found by radar imaging while in orbit. Even with their short lifetimes, the Venera missions each added significant understanding of our sister planet.

Types of Venera probes

{| align="center" class="wikitable"

|+ Venera program probe types

|- align=center style="background: #ddffdd; line-height:120%"

! Model !! Type !! First Launch !! Last Launch !! Missions (success/ total) !! Launch Vehicle !! Mass !! Equipment

| 1VA|| Impact|| 4 Feb 1961 || 12 Feb 1961 || align=center| 0 / 2 || Molniya|| || 5 scientific instruments

| 2MV-1 || style="max-width:0" | Flyby and atmospheric probe|| 25 Aug 1962 || 1 Sep 1962 || align=center| 0 / 2 || Molniya || || 11 scientific instruments

| 2MV-2 ||rowspan="3" | Flyby || 12 Sep 1962 || 12 Sep 1962 || align=center| 0 / 1 || Molniya || || 10 scientific instruments

| 3MV-1 and 1A || 19 Feb 1964 || 2 Apr 1964 || align=center| 0 / 3 || Molniya || || 10 scientific instruments

| 3MV-4 || 12 Nov 1965 || || align=center| 0 / 2 || || || 11 scientific instruments

| 3MV-3 || rowspan="4" | Atmospheric probe and lander || 16 Nov 1965 || 16 Nov 1965 || align=center|0 / 1 || Molniya-M || || 10 scientific instruments

| 1V ||12 Jun 1967 || 17 Jun 1967 || align=center|1 / 2 || Molniya-M || || 8 scientific instruments

| 2V || 5 Jan 1969 || 10 Jan 1969 || align=center|2 / 2 || Molniya-M || || 8 scientific instruments

| 3V || 17 Aug 1970 || 31 Mar 1972 ||align=center| 2 / 4 || Molniya-M || || 5 or 9 scientific instruments

| 4V-1 and 1M || Orbiter and lander || || 4 Nov 1981 || align=center|6 / 6 || Proton-K || || style="max-width:0" | 16 and 21 scientific instruments

| 4V-2 || Orbiter || 2 Jun 1983 || 7 Jun 1983 || align=center|2 / 2 || Proton-K || || style="max-width:0" | 7 scientific instruments with radar

Flight data for all Venera missions

{| class="wikitable sortable" style="margin:auto;"

|- style="background:#efefef;"

!style="padding-left:1px; padding-right:10px;"| Name

!Model

! Mission

!style="padding-left:1px; padding-right:11px;" data-sort-type="usLongDate"| Launch

!style="padding-left:1px; padding-right:11px;" data-sort-type="usLongDate"| Arrival

!style="padding-left:1px; padding-right:15px;" data-sort-type="number" | Survival time <abbr title="minutes">min</abbr>

!class="unsortable"| Results

!style="padding-left:1px; padding-right:12px;"| Image

!style="padding-left:1px; padding-right:19px;"| Lander <abbr title="coordinates">coordin.</abbr>

| Venera 1VA No. 1

|1VA No. 1|| Impactor || 4 February 1961 || || ||Failed to leave earth orbit|| ||

| Venera 1

|1VA No. 2|| Impactor || 12 February 1961 || || ||Communications lost en route to Venus || center|100px|frameless||

| Venera 2MV-1 No.1

|2MV-1 No.1|| Atmospheric probe || 25 August 1962 || || || Escape stage failed; Re-entered three days later ||center|frameless|100x100px||

| Venera 2MV-1 No.2

|2MV-1 No.2|| Atmospheric probe || 1 September 1962 || || || Escape stage failed; Re-entered five days later ||||

| Venera 2MV-2 No.1

|2MV-2 No.1|| Flyby || 12 September 1962 || || || Third stage exploded; Spacecraft destroyed ||||

| Venera 3MV-1 No.2

|3MV-1 No.2|| Flyby || 19 February 1964 || || || Did not reach parking orbit|| ||

| Kosmos 27

|3MV-1 No.3|| Flyby || 27 March 1964 || || || Escape stage failed || ||

| Venera 2

|3MV-4 No.4|| Flyby || 12 November 1965 || || || Communications lost just before arrival || center|frameless|121x121px||

| Venera 3

|3MV-3 No.1|| Atmospheric probe || 16 November 1965 || || || Communications lost just before atmospheric entry. This was the first manmade object to land on another planet on 1 March 1966 (crash). Probable landing region: -20° to 20° N, 60° to 80° E. || ||

| Kosmos 96

|3MV-4 No.6|| Atmospheric probe || 23 November 1965 || || || Failed to leave Earth orbit and reentered the atmosphere. Believed by some researchers to have crashed near Kecksburg, Pennsylvania, USA on 9 December 1965, an event which became known as the "Kecksburg Incident" among UFO researchers. All Soviet spacecraft that never left Earth orbit were customarily renamed "Kosmos", regardless of the craft's intended mission. The name is also given to other Soviet/Russian spacecraft that are intended to—and do reach Earth orbit. || ||

| Venera 4

|4V-1 No.310|| Atmospheric probe || 12 June 1967 ||18 October 1967 || || The first probe to enter another planet's atmosphere and return data. Although it did not transmit from the surface, this was the first interplanetary transmission of any probe. Landed somewhere near latitude 19° N, longitude 38° E. || center|100px ||

| Kosmos 167

|4V-1 No.311|| Atmospheric probe || 17 June 1967 || || || Escape stage failed; Re-entered eight days later

|| ||

| Venera 5

|2V (V-69) No. 330|| Atmospheric probe || 5 January 1969 ||16 May 1969 || 53* || Successfully returned atmospheric data before being crushed by pressure within of the surface. Landed at 3° S, 18° E. || ||

| Venera 6

|2V (V-69) No.331|| Atmospheric probe || 10 January 1969 ||17 May 1969 || 51* || Successfully returned atmospheric data before being crushed by pressure within of the surface. Landed at 5° S, 23° E. || ||

| Venera 7

|4V-1 No. 630|| style="font-weight:bold;" | Lander || 17 August 1970 ||15 December 1970 ||style="font-weight:bold;"| 23 || The first successful landing of a spacecraft on another planet, and the first transmission from another planet's surface. Survived for 23 minutes before succumbing to heat and pressure. ||center|frameless|133x133px||

| Kosmos 359

|3V (V-70)|| Lander || 22 August 1970 || || || Escape stage failed; Ended up in an elliptical Earth orbit || ||

| Venera 8

|4V-1 No.670|| style="font-weight:bold;" | Lander || 27 March 1972 ||22 July 1972 ||style="font-weight:bold;"| 50 || Landed within a radius of 10.70° S, 335.25° E. || ||

| Kosmos 482

|3V (V-72) no. 671|| Probe || 31 March 1972 || || || Escape stage exploded during Trans-Venus injection; Some pieces re-entered and others remained in Earth orbit, until May 2025 where it re-entered the Earth's atmosphere