Editing Ulysses (spacecraft) (section)

== Spacecraft ==
[[File:Parts of Ulysses.jpg|thumb|upright=1.0|right|''Ulysses'' spacecraft]]

The spacecraft was designed by ESA and built by [[Dornier Flugzeugwerke|Dornier Systems]], a German aircraft manufacturer. The body was roughly a box, approximately {{cvt|3.2 × 3.3 × 2.1|m}} in size. The box mounted the {{cvt|1.65|m}} [[dish antenna]] and the [[GPHS-RTG]] [[radioisotope thermoelectric generator]] (RTG) power source. The box was divided into noisy and quiet sections. The noisy section abutted the RTG; the quiet section housed the instrument electronics. Particularly "loud" components, such as the preamps for the radio dipole, were mounted outside the structure entirely, and the box acted as a [[Faraday cage]].

''Ulysses'' was [[Spin-stabilisation|spin-stabilised]] about its z-axis which roughly coincides with the axis of the dish antenna. The RTG, [[whip antenna]]s, and instrument boom were placed to stabilize this axis, with the spin rate nominally at 5 [[Revolutions per minute|rpm]]. Inside the body was a [[hydrazine]] fuel tank. Hydrazine [[monopropellant]] was used for course corrections inbound to Jupiter, and later used exclusively to repoint the spin axis (and thus, the antenna) at Earth. The spacecraft was controlled by eight thrusters in two blocks. Thrusters were pulsed in the time domain to perform rotation or translation. Four [[Sun sensor]]s detected orientation. For fine attitude control, the S-band antenna feed was mounted slightly off-axis. This offset feed combined with the spacecraft spin introduced an apparent oscillation to a radio signal transmitted from Earth when received on board the spacecraft. The amplitude and phase of this oscillation were proportional to the orientation of the spin axis relative to the Earth direction. This method of determining the relative orientation is called [[conical scanning]] and was used by early radars for automated tracking of targets and was also very common in early infrared guided missiles.

The spacecraft used S-band for uplinked commands and downlinked telemetry, through dual redundant 5-watt transceivers. The spacecraft used [[X band|X-band]] for science return (downlink only), using dual 20 watts [[TWTA]]s until the failure of the last remaining TWTA in January 2008. Both bands used the dish antenna with prime-focus feeds, unlike the [[Cassegrain reflector|Cassegrain]] feeds of most other spacecraft dishes.

Dual tape recorders, each of approximately 45-megabit capacity, stored science data between the nominal eight-hour communications sessions during the prime and extended mission phases.

The spacecraft was designed to withstand both the heat of the inner Solar System and the cold at Jupiter's distance. Extensive blanketing and electric heaters protected the probe against the cold temperatures of the outer Solar System.

Multiple computer systems (CPUs/microprocessors/Data Processing Units) are used in several of the scientific instruments, including several radiation-hardened [[RCA 1802|RCA CDP1802]] microprocessors. Documented 1802 usage includes dual-redundant 1802s in the COSPIN, and at least one 1802 each in the GRB, HI-SCALE, SWICS, SWOOPS and URAP instruments, with other possible microprocessors incorporated elsewhere.<ref name="nasa-ulysses-doc-archive">{{Cite web |title=Ulysses NASA Documentation Archive |url=http://ppi.pds.nasa.gov/archive1/ULY_5001/DOCUMENT/ |url-status=dead |archive-url=https://web.archive.org/web/20130317151658/http://ppi.pds.nasa.gov/archive1/ULY_5001/DOCUMENT/ |archive-date=17 March 2013 }}</ref>

Total mass at launch was {{cvt|371|kg}}, of which 33.5&nbsp;kg was [[hydrazine]] propellant used for attitude control and orbit correction.