LAUNCHER SURVEY CONTROL

M270 L

4-116. Although cover and concealment are factors in SCP selection, utility should be the primary consideration. The SCP must be readily accessible so the driver can stop the launcher with the rear edge of the left drive sprocket aligned next to the SCP marker. The area and SCP marker must allow the driver to position the launcher without ground guidance or excessive maneuvering. The SCPs should be collocated with a reload point, if possible. This allows rapid return of the launcher to operational status.

PDS Calibration Referenced in TM 9-1425-648-13&P

4-117. Calibration of the PDS (at least every 30 days, or after replacement of stabilization reference package/position determining system (SRP/PDS), change in operating conditions, or after track or suspension maintenance) corrects for errors caused by differences in track tension or by wear of sprockets and track components. It accounts for the characteristics of each specific launcher. The crew calibrates the launcher PDS, in accordance with the technical manual. The launcher, under specific operating conditions, requires 2 SCPs, 4 to 6 kilometers apart with a straight route of travel between them, located to at least fifth-order accuracy. One point is used to initialize the PDS for location. The launcher is driven to the second SCP at about 40 kilometers per hour, and the first set of calibration corrections is determined. The launcher is then driven back to the starting SCP, where a second set of calibration data is computed. If both sets of calibration data are within tolerance, the system is functional and an averaged set of data is used.

4-118. Calibration is not normally conducted in the platoon OPAREA. The battery operations officer plans the calibration course(s) for the battery as part of his survey plan. Calibrations are normally centrally located behind the firing platoons. A valid calibration can be conducted with any weapon loaded when the appropriate cables (W19 and/or W20) are connected to the pod.

Note: Umbilical cables MUST be connected to the launch pod containers (LPC) while performing calibration.

PDS Update Referenced in TM 9-1425-648-13&P

4-119. Errors that are a function of time and total distance from 11 to 28 minutes for the Army tactical missile system (ATACMS)are corrected by means of PDS updates. The PDS allows an error of up to 0.4 percent of the distance traveled. Crews should update launchers every 6 to 8 kilometers of travel.

SRP Alignment TM 9-1425-648-13&P

4-120. Errors that are a function of time are corrected through the use of periodic SRP realignments.

Realignments are required every 11 to 60 minutes of launcher movement, depending on the munitions type and whether or not the SRP is compensated (see SRP/PDS). If the launcher is moved with the SRP turned off or not stabilized, the position location capability is lost. The system must then be updated at an SCP and the SRP realigned before the launcher can respond to any fire mission requests. Initial alignment of the system takes about 8 minutes. However, allowing the SRP to stabilize 2 ½ additional minutes after “SRP READY” is displayed will increase the time before realignment from 15 minutes to 60 minutes for rocket munitions and from 11 to 28 minutes for the Army tactical missile system (ATACMS).

M142/M270A1 L

Survey Control Points (TM 9-1055-1646-13&P)/(TM 9-1055-647-13&P)

4-121. SCPs are required for M142/M270A1 operations. The exact number depends on the unit SOP because launchers often use SCPs located at reload points. The M142/M270A1 does not require calibration.

If battalion survey assets (PADS) are insufficient to perform the survey requirements expeditiously, an M142/M270A1 launcher can be used to establish SCPs at the entrance to each position area and at the reload point. Establishing and using SCPs allow firing platoons to operate for extended periods (in the inertial mode) if GPS is lost.

M142/M270A1 Navigation

4-122. Vehicle navigation data (easting, northing, altitude, and heading) is determined by the PNU. The PNU will then determine navigation data in the GPS aided mode, the preferred navigation mode. When GPS data is not available, the PNU determines navigation data in the non-aided mode. The PNU gyros continuously measure the angular relationship between the vehicle and true north to determine vehicle heading, which is displayed as the grid azimuth toward which the front of the vehicle is pointed. At the same time, the accelerometers measure the acceleration (motion) of the vehicle in three axes (roll, pitch, and yaw), which is used to determine vehicle easting, northing, and altitude. Data from the vehicle odometer encoders is also used by the PNU in determining location data. The NAV indicator in region 2 of the GDU will appear as a solid box when the launcher is GPS-Aided for navigation. The NAV indicator will appear as broken lines when the launcher is not GPS-Aided for navigation.

Note: Unlike the M270 launcher, the M270A1/M142 is still operational when 1 encoder fails.

4-123. Each time the vehicle stops for at least 2 seconds, the PNU starts a zero velocity update (ZUPT), which removes accumulated errors. The ZUPT takes 40 seconds to complete. If GPS data is available, the PNU will use it along with the gyro and accelerometer data.

4-124. System start-up will always bring the PNU to the aided mode of navigation. Once in the non-aided mode, GPS keys may be entered, which begins the warm or cold start of the GPS receiver in the PNU. The warm/cold start will result in the PNU automatically switching to the GPS aided mode of navigation. As GPS data is lost and reacquired, the PNU will automatically switch between the GPS aided and non-aided modes of navigation.

4-125. When navigating in the GPS aided mode, the location and altitude remain accurate within 10 meters, regardless of distance traveled between latitudes 80 degrees south and 84 degrees north. The ZUPT is performed automatically and no operator prompts are posted. System parameter updates are not required while navigating in this mode. If GPS data is lost and cannot be reacquired within 30 seconds, the PNU switches to the non-aided navigation mode.

M142/M270A1 Non-aided Navigation Mode

4-126. When navigating in the non-aided mode, accuracy is affected by the passage of time, the availability of survey, distance traveled, and operator response to prompts that are posted on the FCP. In the non-aided mode, a ZUPT is required at least every 9 minutes and 30 seconds. A “CNTDN ZUPT TIMER” is posted on the FCP. When the ZUPT countdown timer reaches zero, the advisory “ZUPT REQUIRED” is displayed along with the prompt “STOP LAUNCHER.” A pulsed alarm also sounds as a reminder to stop the launcher.

4-127. When the vehicle has stopped for 2 seconds, “ZUPT IN PROGRESS” is displayed with a 40-second countdown clock. ZUPT requires no operator action other than stopping the launcher. “ZUPT COMPLETE” is displayed when the ZUPT is completed. Once the vehicle moves, the ZUPT countdown timer is displayed. The ZUPT countdown timer only runs when the vehicle is in motion. If the 40-second ZUPT is interrupted, the original ZUPT countdown timer is displayed with whatever time remained prior to stopping.

4-128. When navigating in the non-aided mode, the PNU also requires a system parameter update every 12 kilometers of distance traveled. The prompt “UPDATE SYSTEM PARAMETERS” is posted on the FCP at 12 kilometers distance traveled (DT). An alarm also sounds.

4-129. If ZUPT is performed at 9-minute, 30-second intervals but SCPs are not available for system parameter updates, location and altitude remain accurate within 10 meters for a DT of approximately 40

kilometers. For DT greater than 40 kilometers, the accuracy is 0.04 percent of the DT. If ZUPT is not performed, location and altitude remain accurate within 10 meters for a DT of 6.7 kilometers. For DT greater than 6.7 kilometers, the accuracy is 0.15 percent of the DT. DT is measured from the location at which the PNU entered the non-aided mode or from the location of the last system parameter update. Table 4-2 provides a consolidated list of navigation accuracies and ZUPT times. Table 4-3 lists the alignment times associated with each launcher position.

Operational Considerations

4-130. Hide area operations may degrade or disrupt GPS performance due to line-of-site (LOS) obstruction. (See paragraph 4-108, Hide Area.) If a launcher fails to obtain (or maintain) a GPS signal while in its selected hide area, it should be moved to a more suitable hide location, depending on the tactical situation.

Table 4-2. Navigation

Mode GPS Status ZUPTS Manual Position

Updates Accuracy Aided GPS keys loaded.

4 or 5 satellites.

Prompted–12 km. Within 10 m if ZUPTs.

GPS = global positioning system INOP = inoperational

km = kilometer m = meter

min = minute

PNU = position navigation unit ZUPT = zero velocity update

CAUTION

If launchers with GPS guidance are available, launchers without GPS guidance should not fire ATACMS Block 1A or Block II. The launcher passes the GPS data to the missile before firing, which enables the missile to acquire GPS satellites after launch, thus significantly improving the missile's accuracy. Launchers without GPS guidance should fire only rockets and ATACMS Block 1 until GPS is restored.

However, if a Block 1A/II missile(s) must be fired from a non-GPS aided launcher the missile will be inertially guided and will achieve only ATACMS Block 1 accuracy. This will result in a corresponding decrease in effectiveness, especially at extended ranges.

Table 4-3. Alignment Time

Status Approximate Time

Stationary stored position 5 minutes

Stored position data 2 minutes

Mobile GPS keys must be loaded 15 minutes