Chapter 1 of 5

A leaning arrival

A disrupted orbiter link and an autonomous landing at Utopia

Told in Viking 2’s imagined voice · the events are real · source

First Color Image of the Viking Lander 2 Site
Viking 2My twin had reached Mars. I had a different place to explore.
NASA/JPL
01I am Viking 2, the northern lander of the Viking pair. I launched in September 1975 and entered Mars orbit in August 1976. Orbital photographs helped the team choose Utopia Planitia after the earlier target looked rough. Two landing sites could reveal a planet better than one.
After separation, my orbiter lost its steady Earth-pointing link.
02NASA’s detailed history describes gyro-power trouble and attitude drift on the orbiter. Its computer activated a backup inertial reference, while engineers worked on communications. They still received a small stream of engineering information through the low-gain antenna; this was not three hours of total blindness.
Viking Lander 2 First Picture On The Surface Of Mars http://photojournal.jpl.nasa.gov/catalog/PIA00396
Viking 2My landing computer had to do the flying—not a joystick on Earth.
NASA/JPL
03The lander continued its planned descent using onboard guidance, a heat shield, a parachute and landing engines. Radio delay already made real-time control from Earth impractical. Once the orbiter recovered its reference and link, more mission data and photographs came through.
I reached the ground leaning, but ready to begin.
04On September 3, 1976, I landed at Utopia with a leg resting on a rock. The rocky plain and my tilted body gave my cameras a different view from Viking 1. A successful landing did not need a perfectly level deck—it needed working hardware and useful observations.

The big idea

Autonomous guidance and communications backups solve different problems. Losing a high-rate link does not necessarily mean losing every piece of engineering information.

Think about it

Why does a Mars lander need its own landing plan even when the radio works?

Fact file

Launch
9 September 1975 / 18:39 UT
Titan IIIE-Centaur from Cape Canaveral Launch Complex 41.
Source ↗
Landing
3 September 1976 / Utopia Planitia
Published landing and separation times differ; spacecraft timing and receipt of the signal on Earth are distinct. See the evidence JSON.
Source ↗
Tilt
NSSDCA: 8.2° / NASA Science: 8.5° west
One leg settled on a rock. The exact footpad number and rock dimensions from the draft are not adopted.
Source ↗

In this chapter: Orbiter attitude sensors, backup inertial reference, antennas and the lander’s autonomous descent system

Sources: Main record · Viking 2 Lander · NSSDCA · Viking 2 · NASA Science · Viking 2 Orbiter · NSSDCA

Machine illustration: AI-made. Photos: NASA Image and Video Library, credited on each picture.

Chapter 1 of 5

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