Pointing Control Table (PCT)

General Description

The PCT contains pointing and target selection information for 64 targets. The PCT is shown in Table 5 and described in the paragraphs that follow. The sequencer contains an instruction to select a target. The CC moves the wedges to the wedge positions in the selected target entry thus offsetting the spacecraft pointing to the desired solar coordinates. The sequencer uses the area offsets to define the (DHC) extraction regions for certain frames. The time word and tracking rate parameters are included for possible inclusion of solar rotation tracking. The target identifier appears in telemetry.

Usage Concept

The PCT is 64 words long in order to allow one to group targets according to class and maintain those groupings over a variety of solar and operational conditions. One would dedicate 21 consecutive position to the full sun mosaic. In addition one might dedicate a few consecutive positions to active regions, quiet sun, small mosaic, limb, corona hole, etc. Sequences could then be written that are associated with target class. So say the best active region of the day is always at PCT index 32. Then all active region sequence could set the target to index 32. One need only reload PCT entries rather than sequences to change targets. In addition, the Target Class (TC) field in each PCT entry is used to access the AEC table; thus AEC parameters may have a component that is associated with the target class. TC is also available to the sequence.

PCT Entry	Bits-> Words	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0	0	TID
	1
	2	W1								W2
	3	A1	R1	A2	R2						TC
	4	SRP1
	5	A1RB				A1RO
	6	A1CB				A1CO
	7	SRP2
	8	A2RB				A2RO
	9	A2CB				A2CO
	10	LOBT
	11
1	12-23	Same as 0-10 for wavelength 1
2	24-35	Same as 0-10 for wavelength 2
3-63	36-767	etc.

Table 5 Pointing Control Table

Parameter Descriptions

The paragraphs that follow describe the parameters in the PCT.

Target Identifier (TID)

TID is a 32 bit user defined identifier that appears in housekeeping telemetry and in the science data to identify the current target.

Wedge1 Position (W1)

W1 is the address of guide telescope wedge 1 associated with this target.

Wedge2 Position (W2)

W1 is the address of guide telescope wedge 1 associated with this target

Area1 Enable (A1)

A1 is a single bit field. If set (1), and A1REF in the FDB slaves area1 to the PCT, the sequencer user area1 offset and size parameters from the PCT entry rather than those in the FDB.

Area1 Rotation Tracking (R1)

If R1 is set (1), the area1 offset is adjusted for solar rotation.

Area2 Enable (A2)

A2 is a single bit field. If set (1), and A2REF in the FDB slaves area2 to the PCT, the sequencer user area2 offset and size parameters from the PCT entry rather than those in the FDB.

Area2 Rotation Tracking (R2)

If R2 is set (1), the area2 offset is adjusted for solar rotation.

Target Class (TC)

TC is a 2-bit field that is used in conjunction with the wavelength index to access the Automatic Exposure Control Table. These 2 bits are the upper 2 bits of the AEC index while the wavelength index is the lower 5.

Solar Rotation Period for Area1 (SRP1)

SRP1 is the rotation period for area1. The units are seconds per CCD pixel.

Area1 Row Blocks (A1RB)

If area 1 is slaved to this pointing table entry, the sequencer uses this A1RB rather than the one in the FDB.

Area1 Row Offset (A1RO)

If area 1 is slaved to this pointing table entry, the sequencer uses this A1RO rather than the one in the FDB.

Area1 Column Blocks (A1CB)

If area 1 is slaved to this pointing table entry, the sequencer uses this A1CB rather than the one in the FDB.

Area1 Column Offset (A1CO)

If area 1 is slaved to this pointing table entry, the sequencer uses this A1CO rather than the one in the FDB.

Solar Rotation Period for Area2 (SRP2)

SRP2 is the rotation period for area2. The units are seconds per CCD pixel.

Area2 Row Blocks (A2RB)

If area 2 is slaved to this pointing table entry, the sequencer uses this A2RB rather than the one in the FDB.

Area2 Row Offset (A2RO)

If area 2 is slaved to this pointing table entry, the sequencer uses this A2RO rather than the one in the FDB.

Area2 Column Blocks (A2CB)

If area 2 is slaved to this pointing table entry, the sequencer uses this A2CB rather than the one in the FDB.

Area2 Column Offset (A2CO)

If area 2 is slaved to this pointing table entry, the sequencer uses this A2CO rather than the one in the FDB.

Local On-Board Time (LOBT)

LOBT is the time associated with the area offsets.