The PHT-P filters are located on Change Wheel III (CHW3). Each wheel position is indicated by an integer. In the following table the filter specifications corresponding to a Change Wheel III position have been listed. The values for the spectral resolution ( ${\lambda}_c/{\Delta}{\lambda}$ ) and airy diameter (d_Airy) have been measured in laboratory. The system responses (R_mean) have been derived from in-flight data. The reference central wavelength ( ${\lambda}_{ref}$ ) is defined as a wavelength close to the isophotal centre of the filter, and where possible, matching values given for filters corresponding to other ISO and IRAS instruments (see [20]).

**Table A.1:** Description of the PHT-P filters on CHWIII
Wheel	Filter	${\lambda}_{ref}$	${\lambda}_c/{\Delta}{\lambda}$	R_mean	d_Airy	description
position	ID	( ${\mu}m$ )			('')
1	P1_3p29_UM	3.3	15.160	0.103	2.8	PAH
2	P1_3p6_UM	3.6	3.620	0.127	3.0	Cosmological gap, cf ISOCAM
3	P1_4p85_UM	4.8	3.140	0.152	4.1	Continuum
4	P1_7p3_UM	7.3	2.190	0.212	6.2	Continuum
5	P1_7p7_UM	7.7	9.320	0.194	6.4	PAH
6	P1_10_UM	10	5.551	0.177	8.4	sillicate feature
7	P1_11p3_UM	11.3	14.070	0.177	9.5	PAH
8	P1_12p8_UM	12.8	5.330	0.089	10.8	Continuum
9	P1_16p0_UM	15	1.820	0.130	13.8	Continuum
10	P1_11p5_UM	12	5.550	0.156	10.0	IRAS 12 ${\mu}m$ cf. ISOCAM
11	P2_20_UM	21.03	2.330	0.324	17.7	Close to Q band
12	P2_25_UM	25	2.610	0.370	20.0	IRAS 25 ${\mu}m$
13	P3_60_UM	60	2.350	0.111	50.3	IRAS 60
14	P4_100_UM	100	2.590	0.303	83.9	IRAS 100

The PHT-P apertures are located on the inner circle of Change Wheel II (CHW2). Each wheel position is indicated by an integer. In the following table the aperture specifications corresponding to a Change Wheel II position have been listed.

**Table A.2:** Description of the PHT-P apertures located on CHWII
Wheel	Aperture	Diameter	Area	Solid Angle	description
position	ID	('')	(mm²)	(10^-8 ster)
1	52_SEC	52	4.1548	5.13	circular 2.3 mm
2	79_SEC	79	9.0792	11.21	circular 3.4 mm
3	99_SEC	99	14.522	17.93	circular
4	120_SEC	120	21.237	26.22	circular
5	127 $\times$ 127_SEC	127 $\times$ 127	30.250	37.3	square
6	180_SEC	180	48.398	59.8	circular
7	180_SEC_XBLK				not used
8	5_SEC	5	0.0314	0.039	circular
9	7p6_SEC	7.6	0.1001	0.124	circular
10	10_SEC	10	0.1735	0.214	circular
11	13p8_SEC	13.8	0.2827	0.349	circular
12	18_SEC	18	0.5218	0.625	circular
13	20 $\times$ 32_SEC	20 $\times$ 32	1.1288	1.39	rectangular
14	23_SEC	23	0.7854	0.97	circular

A.1.3 PHT-C Filters

The PHT-C filters are located in the outer circle of Change Wheel II (CHW2). In the following table the filter specifications corresponding to a Change Wheel II position have been listed. The values for the spectral resolution ( ${\lambda}_c/{\Delta}{\lambda}$ ) and point spread function factor (f_psf) have been measured in laboratory. The system responses (R_mean) have been derived from in-flight data. The reference wavelength ( ${\lambda}_{ref}$ ) is defined as a wavelength close to the isophotal centre of the filter, and where possible, matching values are given for filters corresponding to other ISO and IRAS instruments (see [20]).

The point spread function factor represents the fraction of the power in the beam falling on the whole detector array if the beam is centered on the array (the values have been derived from in-flight data, see section 9 for an explanation). The geometrical solid angles of the pixels are slightly filter dependent, their averages are:

${\Omega}_{C100}$ = 0.0688 ${\times}10^{-6}$ sr
${\Omega}_{C200}$ = 0.281 ${\times}10^{-6}$ sr

**Table A.3:** Description of the PHT-C filters on CHWII
Wheel	Filter	${\lambda}_{ref}$	${\lambda}_c/{\Delta}{\lambda}$	R_mean	f_psf	description
position	ID	( ${\mu}m$ )			('')
1	C100_OPEN					not used
2	C100_90_RED	90	1.730	0.296	0.900	wide band cont.(backup)
3	C100_50_UM	65	1.130	0.045	0.912	continuum
4	C100_60_UM	60	2.510	0.130	0.918	continuum IRAS 60 ${\mu}m$
5	C100_70_UM	80	1.670	0.121	0.902	continuum
6	C100_100_UM	100	2.180	0.270	0.892	continuum IRAS 100 ${\mu}m$
7	C100_105_UM	105	2.790	0.236	0.884	continuum
8	C100_90_UM	90	1.690	0.296	0.900	wide band continuum
9	C200_160_UM	170	1.940	0.431	0.708	wide band continuum
10	C200_200_UM	200	3.550	0.215	1.054	continuum
11	C200_180_UM	180	2.630	0.327	0.972	continuum
12	C200_135_UM	150	1.910	0.260	0.668	continuum
13	C200_120_UM	120	2.400	0.131	0.574	continuum
14	C200_RETICLE	0.00	0.00	0.00	0.00	not used

A.1.4 Other Filterwheel Components

Change Wheel I (CHW1) is either used to redirect the light to the next optical component such as PHT-S, the inner Change Wheel II and the outer Change Wheel II, or is used to put a polariser in the beam. In the following table the specifications corresponding to a Change Wheel I position have been listed.

**Table A.4:** Description of CHWI
Wheel	Element	description
position	ID
1	PHT_P_POL000	PHT P Polariser $0{\deg}$
2	PHT_P_POL120	PHT P Polariser $120{\deg}$
3	PHT_P_POL240	PHT P Polariser $240{\deg}$
4	PHT_P_NO_POL	PHT P Flat mirror
5	PHT_S	PHT S Flat mirror
6	PHT_C_RETICL	PHT C C-cut Quartz
7	PHT_C_FREE1	PHT C Free aperture
8	PHT_C_FREE2	PHT C Free aperture
9	PHT_C_FREE3	PHT C Free aperture
10	PHT_S_REDUND	PHT S Flat mirror (redundant)
11	PHT_C_POL000	PHT C Polariser $0{\deg}$
12	PHT_C_POL120	PHT C Polariser $120{\deg}$
13	PHT_C_POL240	PHT C Polariser $240{\deg}$
14	PHT_C_NO_POL	PHT C Free aperture

A.1 Mean Filter/Aperture Specifications

A.1.1 PHT-P Filters

A.1.2 PHT-P Apertures

A.1.3 PHT-C Filters

A.1.4 Other Filterwheel Components