How To ARRT - MOARdV/MOARdVPlus GitHub Wiki

The Altitude / Range-Range Rate instrument provides feedback during landing (and, optionally, launch) operations, as well as during rendezvous / docking operations in orbit.

The ARRT subsystem consists of the ARRT power switch, the ARRT mode selector switch, the ARRT error flag indicator, and the ARRT instrument. Note: the illustration above shows a combined power / mode switch. More recent IVAs use separate switches.

ARRT Power Switch

The ARRT instrument is inactive until the power switch (ARRT) is switched to the ON position.

ARRT Mode Switch

The ARRT Mode switch (MODE) selects the mode the display is operating in:

• ALT: The ARRT is in Radar Altimeter mode. The ALT and ALT RATE legends are illuminated. The RANGE/ALT strip displays altitude above ground, and the RANGE RATE/ALT RATE strip displays vertical speed based on radar telemetry. The instrument is inactive until a valid radar altimeter signal is received at approximately 5km above the surface.
• RNG: The ARRT is in Range / Range Rate mode. The RANGE and RANGE RATE legends are illuminated. If there is a target, the RANGE/ALT strip displays the distance from the target, while the RANGE RATE/ALT RATE strip displays relative speed. If there is no target, the strips return to zero.

ARRT Error Flag Indicator

The ARRT Error flag (ARRT ERR) indicates when the MODE switch is set to RNG (range) and there is no target currently being tracked.

ARRT Data Display

The ARRT data display consists of two vertical bar strips. The left strip has the legend RANGE/ALT. It displays the range to target or altitude above ground as specified by the mode switch. This strip can report distances of up to 5000 meters. The right strip has the legend RANGE RATE/ALT RATE. It provides the closure/departure rate to the target or the vertical speed, depending on the mode.