Vega 2

Chronology

Mission timeline

1. December 21, 1984, 09:13:52 UTC

   Launch

   Launched on a Proton from Baikonur Cosmodrome

   The launch/orbital information page prints Launch Date/Time: 1984-12-21T09:13:52Z, Launch Vehicle: Proton and Launch Site: Tyuratam (Baikonur Cosmodrome), U.S.S.R, and the master catalog prints the same vehicle and site in Facts in Brief. The master catalog's own text says two identical spacecraft, Vega 1 and Vega 2, were launched December 15 and 21, 1984, respectively.

   Earth
2. June 15, 1985

   Deployment

   Balloon aerostat deployed into the middle cloud layer

   The balloon page records that the balloon package was pulled out of its compartment by parachute 40 seconds later at 61 km altitude, at 7.45 degrees S, 179.8 degrees east, that a second parachute opened at an altitude of 55 km, 200 seconds after entry, extracting the furled balloon, that the balloon was inflated 100 seconds later at 54 km and the parachute and inflation system were jettisoned, and that the balloon floated back to a stable height between 53 and 54 km some 15 to 25 minutes after entry, with a mean stable height of 53.6 km. Carried at day precision because every clause that prints one of these times prints no date beside it; the day is the one the same page gives for the capsule's entry. THE PAGES DISAGREE ON THE FLOAT ALTITUDE: the bus and descent craft pages both say the aerostat floated at approximately 50 km altitude. The descent craft page also disagrees with the balloon page on the hardware: it says the balloon supported a total mass of 25-kg with a 5-kg payload hung suspended 12 meters below it, where the balloon page gives a total deployed mass of 21.5 kg with a 6.9 kg gondola on a 13 meter long tether strap.

   Venus
3. June 15, 1985

   Gravity assist

   Venus swingby retargets the bus for Comet Halley

   The master catalog records that after deploying the descent module the Vega 2 bus flew by Venus on June 15, 1985, and that the spacecraft was retargetted using Venus gravity field assistance to intercept Comet Halley in March 1986; the descent craft page repeats that the flyby spacecraft was then retargetted using Venus gravity assistance. No cited page prints a flyby distance for this spacecraft, which is the mirror of its twin: Vega 1's page prints 39,000 km and no date.

   Venus
4. June 15, 1985, 01:59:30 UTC

   Milestone

   Descent craft enters the atmosphere of Venus

   The descent craft page records that after separation from the Vega 2 spacecraft the lander entered the Venus atmosphere on 15 June 1985 at 01:59:30 UT at 10.80 km/s with an entry angle of 19.08 degrees, that the pilot parachute was deployed at an altitude of 65 km and the braking parachute opened 11 seconds later at 64.5 km, and that the upper heat protection hemisphere was released at this time and the lower hemisphere 4 seconds later at 64.2 km. THE TWO PAGES DISAGREE ON THE ENTRY TIME: the balloon page dates the same capsule's entry to 2:06:04 UT, which it labels Earth received time, and gives the entry altitude as 125 km and the speed as roughly 11 km/sec. Neither figure is reconciled here; the descent craft's own page is followed because the timestamp is the one printed with a full date beside it.

   Venus
5. June 15, 1985, 03:00:50 UTC

   Landing

   Descent craft lands in eastern Aphrodite Terra

   The descent craft page records that the lander touched down at 03:00:50 UT on 15 June 1985 at 8.5 S, 164.5 E, in eastern Aphrodite Terra, that the altitude of the touchdown site was 0.1 km above the planetary mean radius, and that the measured pressure at the landing site was 91 atm and the temperature was 736 K. It also records that the surface sample was found to be an anorthosite-troctolite. Its own launch/orbital information page prints a Lander row with Central Body Venus and Lander Coordinates matching the descent craft page's latitude and longitude, and an Epoch start (UTC) of 1985-06-15 01:59:30, which is the atmospheric entry instant this record carries at vega-2-descent-craft-entry rather than the touchdown. That page also prints Decay Date: 1985-06-14, a day before the entry and landing the descent craft page narrates.

   Venus
6. March 1986

   Flyby

   Comet Halley encounter at 77.7 km/s

   The master catalog records that the first spacecraft encountered Comet Halley on March 6, 1986, and the second three days later, that the flyby velocity was 77.7 km/s, and that although the spacecraft could be targetted with a precision of 100 km, the position of the spacecraft relative to the comet nucleus was estimated to be known only to within a few thousand kilometers, which together with the problem of dust protection led to estimated flyby distances of 10,000 km for the first spacecraft and 3000 km for the second. No bodyId is carried because Comet Halley is not a committed body in this catalog. Carried at month precision because the only date the page prints for this spacecraft's encounter is three days later than the first spacecraft's March 6, 1986, which is arithmetic over a printed date rather than a reading; March 1986 is what the page prints for the interception itself.

7. Date unknown

   Deployment

   Descent module separates two days before arrival

   The descent craft page records that the lander separated from the Vega 2 spacecraft two days before arrival at Venus and entered the planet's atmosphere on an inclined path, without active maneuvers, as was done on previous Venera missions, and the master catalog says only that the bus flew by Venus after deploying the descent module. Carried without a timestamp because no cited page prints a date for the separation, which is where this record and its twin's diverge: Vega 1's master catalog prints June 9, 1985 for the same manoeuvre.

   Venus
8. Date unknown

   Loss of contact

   Balloon's final transmission, after 11,100 km

   The balloon page records that the probe crossed the terminator from night to day at 9:10 UT on 16 June after traversing 7400 km, that it continued to operate in the daytime until the final transmission was received at 00:38 UT on 17 June from 7.5 S, 76.3 E after a total traverse distance of 11,100 km, and that it is not known how much further the balloon travelled after the final communication. Carried without a timestamp because the sentences that print those two days print no year. THE PAGES DISAGREE ON THE LIFETIME: the bus and descent craft pages give the balloon a 47-hr lifetime and the balloon page about 46 hours.

   Venus

Mission architecture

Vehicles

• Vega 2 Spacecraft · Spacecraft · completed

  Destinations: Venus

  • Vega 2 Descent Craft · Lander · completed

    Destinations: Venus

    • Vega 2 Balloon · Probe · completed

      Destinations: Venus