[FPSPACE] 25th Anniversary of First Direct Surface Images of Venus

[Larry Klaes]

Three space probe anniversaries of note for the week of
October 20-25, 2000:


30th Anniversary: Zond 8 was lofted by the USSR into space
on October 20, 1970, on the last of the Zond lunar missions 
to test a modified Soyuz spacecraft for the Soviet manned 
exploration of Earth's moon in direct competition with the
USA Apollo program - though by then the lunar race was
considered won by the US two years earlier with Apollo
8 and 11.

The mission was successful in looping around Luna four days 
later and taking images of the lunar surface and Earth, but 
Zond 8 re-entered Earth's atmosphere on October 26 at such 
a steep angle that any cosmonauts on board probably would 
have been killed or at the least seriously injured.

Some URLs on Zond 8:

http://www.friends-partners.org/~mwade/craft/soyz7kl1.htm

http://www.users.wineasy.se/svengrahn/radioind/Zondradio/Zondrad.htm

http://www.interaxs.net/pub/spacey/sovspac1.htm


25th anniversary:  The first images ever taken from and of
the surface of another planet, in this case the planet Venus
by the USSR Venera 9 and 10 landers on October 22 and 25,
1975, respectively, after a four-month journey through space.

Granted, the USSR Mars 3 lander began to take images of the
surface of Mars in late 1971 after an initially successful
landing on the Red Planet, but the lander transmissions were
lost 90 seconds after touchdown and what little image was 
returned was apparently of no real use.

The following is excerpted from the article "The Robot
Exploration of Venus, Part I" from Issue 8:1 (2000) of 
Quest: The History of Spaceflight Quarterly magazine:

http://www.spacebusiness.com/quest/


The Face of Hell Revealed 
 
Exploration of Venus by Soviet spacecraft got back into full swing 
by the launch window of 1975.  As predicted, the more advanced second
generation of VENERA vehicles were to be the latest emissaries from 
Earth.  In basics, these new machines were similar in design to their 
Soviet predecessors, consisting of a main bus with large solar panels 
on either side and an attached lander (inside a protective aeroshell) 
for making surface studies.  Here, though, the resemblance abruptly 
ended. 
 
The two vessels, to become known as VENERA 9 and 10, carried far 
more instrumentation than any such spacecraft before.  The result 
of these improvements were to make the new VENERAs the biggest and 
heaviest Venus probes yet built.  

The complete VENERA 9 craft measured 6.7 meters (22.11 feet) across 
with the solar panels extended.  The probe weighed a total of 4,936 
kilograms (10,859 pounds), with 660 kilograms (1,452 pounds) of that 
being the improved lander.  VENERA 10 weighed 97 kilograms (213 pounds) 
more overall.  The increased mass forced the Soviets to switch from 
using the old MOLNIYA rockets to the more modern and powerful PROTON 
boosters, which had already proven themselves as heavy lift vehicles 
on Luna and Mars missions.
 
The main buses of the two VENERAs would neither fly by the planet 
nor plunge into the turgid atmosphere to their destruction.  Instead, 
they would become the first space vehicles to circle the second world.  

The orbiters were equipped to image the planet's cloud cover, along 
with measuring its brightness, reflectivity, and temperature.  Other 
devices were carried to search for any evidence of even a minute 
planetary magnetic field.  The VENERA buses had the additional task 
of sending data from the deployed landers back to Earth. 
 
The landers underwent a series of major technical changes that gave 
the Venus explorers the unusual appearance of a sphere with a top hat 
and a wide ring (torus) surrounding the base of the ball.  
 
The "top hat" served a multitude of purposes: The vertical cylinder 
housed the parachute and served as the core that the main antenna was 
coiled around.  The disc underneath the cylinder and overhanging the 
sphere was used both as a reflector of radio waves to the antenna and 
as an air brake for the landers during the last stages of their descent 
through the Venerean sky.

Past VENERA missions had proven that Venus' atmosphere was so thick 
that an oblate object could sink slowly enough to the planet's roasting 
surface without the aid of parachutes and survive the impact.  This 
method also allowed the lander to reach the surface fast enough so 
as not to overheat while still high in the atmosphere. 
 
The metallic sphere housed the majority of the probes' scientific 
instruments, including an extendible radiation densitometer to measure 
the soil density and a television imaging system to give humanity its 
first optical views of Venus' elusive surface.  Just below the cameras 
were floodlights to illuminate what Soviet scientists thought would be 
a very dim landscape, due to the information from VENERA 8 three years 
prior.  The torus at the bottom would cushion the physical shock of 
the craft at the moment of touchdown and keep the lander upright.
 
VENERA 9 and 10 were launched into space on June 8 and 14, 1975, 
respectively.  Four months later and two mid-course corrections apiece, 
the robot vehicles arrived in Venerean space.  On October 20, 1975, 
VENERA 9 split into two components: The main bus fired its braking 
engines to achieve a wide orbit around Venus, while the capsule was 
targeted for a planetary landing.
 
On October 22, the VENERA 9 lander entered the atmosphere of Venus.  
The descent pattern for the probe varied some from the landers before 
it.  Once air resistance had slowed down the craft, the top half of 
the lander's spherical covering was pulled away at an altitude of 
sixty-four kilometers (thirty-eight miles) by two small parachutes.  
A braking parachute then emerged to further reduce VENERA 9's velocity. 
 
Soon after this procedure, three main parachutes were sent billowing 
above the lander, while the lower section of the aeroshell was released 
from the probe, completely exposing the lander to the surrounding air. 
 This profile lasted for twenty minutes.  Fifty kilometers (thirty miles)
above the planet's surface, VENERA 9 broke through the dense cloud cover 
and removed its main parachutes.  The lander now had to rely on its 
aerobrake disc to survive impending contact with the swiftly 
approaching ground. 
 
At 5:13 Greenwich Mean Time (GMT), the strange-looking craft touched 
down at the base of a hill in northeastern Beta Regio at a speed of 
seven meters (twenty-three feet) per second, kicking up a small cloud 
of dust upon landing.  Initial temperature and pressure readings in 
the immediate area reached 460 degrees Celsius (860 degrees Fahrenheit) 
and ninety Earth atmospheres.  Winds at the landing site blew around 
VENERA up to 2.5 kilometers (1.5 miles) per hour.  While a similar 
breeze on Earth would be quite mild, Venus' denser atmosphere 
amplified the force of the wind several times. 
 
Fifteen minutes into its surface mission, VENERA 9's television 
cameras were automatically uncovered and activated, where they began 
a scan of the landing site in a forty by 180-degree field of view.  
The curved black, white, and gray image eventually transmitted to 
Earth was the first of its kind ever to be returned by a spacecraft 
on another planet.  It was also a very surprising picture to the 
scientists who had assumed that the Venerean crust would be little 
more than a desert of nearly unbroken sand engulfed in darkness. 
 
VENERA 9's new home was as brightly lit as an overcast day on Earth 
(the Sun shone fifty-four degrees above the local horizon during the 
lander's fifty-three minutes of transmission time), rendering the 
floodlights unnecessary.  The ground was certainly not a bland sea 
of sand.  Both sharp and round-edged rocks embedded in soil surrounded 
the craft off into the distance, indicating that this region may have 
seen relatively recent crustal activity.  This was yet another 
surprise to scientists who thought that Venus had been geologically 
extinct for ages.  The lander also captured part of its shock-absorbing 
torus and the extended densitometer in the lower portion of the historic
image. 
 
The findings from the probe's gamma-ray spectrometer produced yet 
another new piece of information to the data sent back by VENERA 8 
in 1972.  This particular area appeared to be composed of a more 
common basaltic material than that found at VENERA 8's landing zone 
in Navka Planitia.  Later Venus missions have shown that Beta Regio 
consists of two shield volcanoes, possibly still active. 
 
On October 25, 1975, VENERA 10 followed a programmed route similar to 
that of its twin vessel.  The main bus inserted itself into a two-day 
orbit around Venus while the lander fell onto the planet 2,200 kilometers
(1,320 miles) from the now silent VENERA 9, in the southeastern corner 
of Beta Regio.  The craft found its examination site to be five degrees 
warmer and two bars of air pressure higher than its counterpart's 
landing area.  The winds moved at 1.3 meters (4.3 feet) per second. 
 
VENERA 10 came to rest at a slight angle on a large, flattened rock.  
The landscape image produced by the vehicle was quite different from 
its immediate predecessor's.  The entire plain consisted of rock slabs 
and soil which appeared weathered and truly ancient, with little 
evidence of any geological activity having occurred in a very long 
time. Despite this, composition analysis of the surface by VENERA 10 
did agree with VENERA 9, the primary soil mineral being a common type
of basalt. 
 
The VENERA 10 lander transmitted twelve more minutes of information 
than did VENERA 9, though both craft may have been active even longer.  
The signals were cut by the orbiter relays when they went out of the 
landers' radio range during the surface missions.  
 
The orbiters themselves continued to return data through the middle 
of 1976, monitoring solar wind interactions on Venus' ionosphere and 
newly discovered plasma tail.  The probes showed that liquid droplets 
existed in the atmosphere, though their actual composition remained 
to be learned.  Infrared radiation measurements on Venus' clouds 
indicated that the world's nighttime temperatures were actually warmer 
than in the day hemisphere!  Strong air streams on Venus' daylight 
half brought radiating elements to heat the dark side.  The orbiters 
also found short-period glows in the night hemisphere that were 
attributed to bursts of lightning. 
 
So much new information had been returned about the veiled world by 
VENERA 9 and 10 that the Soviets were forced to skip the Venus launch 
window in the winter of 1976-1977.  Extra time was required to modify 
the next group of second generation VENERA spacecraft to better examine 
the planet's latest revelations and mysteries. 


A bunch of relevant URLs:

http://www.friends-partners.org/~mwade/craft/venra4v1.htm

http://nssdc.gsfc.nasa.gov/nmc/tmp/1975-050D.html

http://nssdc.gsfc.nasa.gov/nmc/tmp/1975-054D.html

http://nssdc.gsfc.nasa.gov/imgcat/html/group_page/VN.html

http://www.solarviews.com/cap/venus/venera9.htm

http://www.terra.es/personal/heimdall/eng/venus9-10.htm

http://zebu.uoregon.edu/~js/ast121/lectures/surface_venus.html

http://wald.heim.at/urwald/540029/venus.htm

http://www.donaldedavis.com/CHANGING/STUFF.html

http://www.donaldedavis.com/PARTS/VENERMOD.jpg

http://delcano.mit.edu/venera/

http://vsm.host.ru/e_venera.htm

http://sunra.colorado.edu/david/ch3.html

http://top.pefri.hr/seminari/suncev_sustav/venera/venera.html

http://www.bezso.ch/bezso.ch/astronomie/sovvenus.htm

http://www-ssc.igpp.ucla.edu/personnel/russell/papers/interact_solwind/

http://www-ssc.igpp.ucla.edu/personnel/russell/papers/evidence/

http://www.seds.org/pub/info/newsletters/ejasa/1993/jasa9303.txt

http://www.ninfinger.org/~sven/models/sovietsp/venera.html

http://www.ninfinger.org/~sven/models/html_pix/ussr_unman.html

http://www.ucl.ac.uk/geolsci/edu/students/planet/student/work/venus.htm

http://www.kilim.com.tr/astro/v-surf.html

http://www.geology.uiuc.edu/~hsui/classes/geo116/lectures/venus.html

http://www.space.com/news/spacehistory/greatest_70s_991230.html

http://www.seds.org/nineplanets/nineplanets/venus.html


Larry