# IV. 2MASS Data Processing

## 6. Position Reconstruction

Table 1: Pointing Reconstruction Definitions

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B-scan  = Band scan system (Refers collectively to J-scan, H-scan and/or K-scan)
DxJ2H   = J-band to H-band cross-scan difference for scan
DxJ2H_0 = A priori estimate of J-band to H-band cross-scan difference for scan
DxJ2K   = J-band to K-band cross-scan difference for scan
DxJ2K_0 = A priori estimate of J-band to K-band cross-scan difference for scan
DxR1    = U-scan x position difference for Read1 frames
DyJ2H   = J-band to H-band in-scan difference for scan
DyJ2H_0 = A priori estimate of J-band to H-band in-scan difference for scan
DyJ2K   = J-band to K-band in-scan difference for scan
DyJ2K_0 = A priori estimate of J-band to K-band in-scan difference for scan
DyR1    = U-scan y position difference for Read1 frames
FRAME   = Single freeze point during scan (includes J1,J2, H1,H2, K1,K2 frames)
H-frame = Refers collectively to H1 and H2 frames
H-scan  = H-band scan system defined by H2-frame system of first frame of scan
H1-frame= System attached to each H1 frame (origin at SE corner;+y~N,+x~W)
H2-frame= System attached to each H2 frame (origin at SE corner;+y~N,+x~W)
HFxHni  = H-frame x coordinate H-band source number "i" in FRAME number "n"
HFyHni  = H-frame y coordinate H-band source number "i" in FRAME number "n"
J-frame = Refers collectively to J1 and J2 frames
J-frame = Refers collectively to K1 and K2 frames
J-scan  = J-band scan system defined by J2-frame system of first frame of scan
J1-frame= System attached to each J1 frame (origin at SE corner;+y~N,+x~W)
J2-frame= System attached to each J2 frame (origin at SE corner;+y~N,+x~W)
JFxJni  = J-frame x coordinate J-band source number "i" in FRAME number "n"
JFyJni  = J-frame y coordinate J-band source number "i" in FRAME number "n"
K-scan  = J-band scan system defined by K2-frame system of first frame of scan
K1-frame= System attached to each K1 frame (origin at SE corner;+y~N,+x~W)
K2-frame= System attached to each K2 frame (origin at SE corner;+y~N,+x~W)
KFxKni  = K-frame x coordinate K-band source number "i" in FRAME number "n"
KFyKni  = K-frame y coordinate K-band source number "i" in FRAME number "n"
N-scan  = Nominal scan system (y-axis points N along of-date meridian,+x W)
PosFrm  = Position-of-Frames processor which reconstructs frame positions
PosPts  = Position-of-Points processor which reconstructs point-source positions
RS      = Reference star
SXH     = Cross-scan scale factor used to convert from H-frame to U-scan
SXH_0   = A priori est. of x-scan scale factor to convert from H-frame to U-scan
SXJ     = Cross-scan scale factor used to convert from J-frame to U-scan
SXJ_0   = A priori est. of x-scan scale factor to convert from J-frame to U-scan
SXK     = Cross-scan scale factor used to convert from K-frame to U-scan
SXK_0   = A priori est. of x-scan scale factor to convert from K-frame to U-scan
SYH     = In-scan scale factor used to convert from H-frame to U-scan
SYH_0   = A priori est. of in-scan scale factor to convert from H-frame to U-scan
SYJ     = In-scan scale factor used to convert from J-frame to U-scan
SYJ_0   = A priori est. of in-scan scale factor to convert from J-frame to U-scan
SYK     = In-scan scale factor used to convert from K-frame to U-scan
SYK_0   = A priori est. of in-scan scale factor to convert from K-frame to U-scan
TH      = Rotation angle of H-band detector array w.r.t. scan direction
TH_0    = A priori est. of rot. angle of H-band detector array w.r.t. scan dir.
TJ      = Rotation angle of J-band detector array w.r.t. scan direction
TJ_0    = A priori est. of rot. angle of J-band detector array w.r.t. scan dir.
TK      = Rotation angle of K-band detector array w.r.t. scan direction
TK_0    = A priori est. of rot. angle of K-band detector array w.r.t. scan dir.
U-scan  = Universal scan system (y-axis along scan path toward ~N; x points ~W)
USxHni  = U-scan x position of H-band source number "i" in FRAME number "n"
USxJCn0 = U-scan x position of J2-frame center for FRAME number "n"
USxJni  = U-scan x position of J-band source number "i" in FRAME number "n"
USxKni  = U-scan x position of K-band source number "i" in FRAME number "n"
USyHni  = U-scan y position of H-band source number "i" in FRAME number "n"
USyJCn0 = U-scan y position of J2-frame center for FRAME number "n"
USyJni  = U-scan y position of J-band source number "i" in FRAME number "n"
USyKni  = U-scan y position of K-band source number "i" in FRAME number "n"
cxR1_0  = A priori est. of Read1 x-scan difference at FRAME zero
cyR1_0  = A priori est. of Read1 in-scan difference at FRAME zero
dDxJ2H  = Small adjustment to J-band to H-band cross-scan difference for scan
dDxJ2K  = Small adjustment to J-band to K-band cross-scan difference for scan
dDyJ2H  = Small adjustment to J-band to H-band in-scan difference for scan
dDyJ2K  = Small adjustment to J-band to K-band in-scan difference for scan
dSXH    = Small adj. to x-scan scale factor to convert from H-frame to U-scan
dSXJ    = Small adj. to x-scan scale factor to convert from J-frame to U-scan
dSXK    = Small adj. to x-scan scale factor to convert from K-frame to U-scan
dSYH    = Small adj. to in-scan scale factor to convert from H-frame to U-scan
dSYJ    = Small adj. to in-scan scale factor to convert from J-frame to U-scan
dSYK    = Small adj. to in-scan scale factor to convert from K-frame to U-scan
dTH     = Small adjustment to rot. angle of H-band detector w.r.t. scan dir.
dTJ     = Small adjustment to rot. angle of J-band detector w.r.t. scan dir.
dTK     = Small adjustment to rot. angle of K-band detector w.r.t. scan dir.