Globus IMP instruments

 Introduction:-

Globus IMP instruments were spacecraft navigation instruments used in Soviet and Russian crewed spacecraft. The IMP acronym stems from the Russian expression Indicator of position in flight, but the instrument is informally referred to as the Globus. It displays the nadir of the spacecraft on a rotating terrestrial globe. It functions as an onboard, autonomous indicator of the spacecraft's location relative to Earth coordinates. An electro-mechanical device in the tradition of complex post-World War II clocks such as master clocks, the Globus IMP instrument incorporates hundreds of mechanical components common to horology. This instrument is a mechanical computer for navigation akin to the Norden bombsight. It mechanically computes complex functions and displays its output through mechanical displacements of the globe and other indicator components. It also modulates electric signals from other instruments.

Design and purpose:-

        The Voskhod spacecraft was the second generation of spacecraft designed in the crewed Soviet space program, essentially an adaptation of the earlier Vostok spacecraft. It flew two crewed missions, Voskhod 1 (world's first multi-crewed mission, launched on 12 October 1964) and Voskhod 2 (featuring the world's first Extra-vehicular activity, or EVA, commonly called a spacewalk, launched on March 18, 1965). The Voskhod spacecraft—and its Globus IMP instruments—is a close derivative of Vostok, which flew six Soviet individuals to low Earth orbit, including the world's first human in space, Yuri Gagarin, and the world's first woman in space, Valentina Tereshkova. The main difference between IMP versions 1 and 2 (Vostok spacecraft) and later versions (Voskhod and Soyuz) is the addition of the disc-shaped longitude and latitude indicators.

The design objectives for the IMP were to compute and display the geographic coordinates at the spacecraft's nadir, i.e. which point on Earth's surface it was overflying. The Globus displayed this data to the crew, and also transmitted electrical data to other systems through a variable resistance and cam-activated switching.

Derivatives of Vostok's and Voskhod's IMP have been flown on every Soyuz spacecraft up to the last of the Soyuz TM mission in April 2002. The main functional addition to IMP versions designed for Soyuz was the ability to manually change the orbit inclination. On Vostok and Voskhod, the inclination to the equator had been constant at 65 degrees by virtue of the booster design limitations and the geographical location of the Baikonur Cosmodrome from which every Soviet and Russian crewed mission had been launched to date, so there was no need to implement inclination modulation into versions 1 to 4 of the IMP.

The Soyuz TMA spacecraft and its successors now provide similar functions to the Globus using a computerized world map on a computer display.

The Russian early missions were mostly automated and controlled from the mission control center (the TsUP). The spacecraft essentially controlled itself, and the cosmonauts were expected to initiate maneuvers or corrections only after approval from the MCC and according to its data and parameters. Therefore, the instrumentation available to the pilot was minimal and its operational relevance was limited to contingency scenarios as much as possible. The readings from the IMP were primarily intended to help cosmonaut pilots confirm that the automated flight sequencer was operating normally. The data would also keep the crew aware of their position when they were orbiting over the nighttime part of the Earth, or when the spacecraft's viewports and Vzor periscope couldn't be pointed toward the ground.

However, the IMP would become crucial if manual retrorocket activation became compromised by failure of either the flight sequencer or communications with mission control, as did happen on Voskhod 2. Furthermore, given the scarcity of Soviet communication stations on Earth, the cosmonauts spent most of their time out of range with ground control and needed instruments to assess their position relative to the ground.

By contrast, the US crewed space programs used a similar, mechanical positional indicator only during two of its early Mercury missions before discarding it (and using its former niche in Mercury's instrument panel as an equivalent to a car's glove compartment). The American instrument was a crude, smaller equivalent to the Soviets', an all-mechanical device (hand-wound) of limited complexity. Given the more extensive radio communication network with the spacecraft afforded by NASA, all subsequent crewed missions, including lunar Apollo missions and Space Shuttle missions, used onboard maps, ground telemetry and more recently, computerized maps on portable laptop computers to provide the astronauts with positional information.

                                                                    source:-wikipedia.org