The PHT-P filters were located on Change Wheel III (CHW3). Each wheel position is indicated by an integer. In Table A.1 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 ( $d_{Airy}$ ) were measured in the laboratory. The system responses ( $R_{mean}$ ) were 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 Moneti, Metcalfe & Schulz 1997, [39]).

**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	15.16	0.103	2.8	PAH
2	P1_3p6_UM	3.6	3.62	0.136	3.0	Cosmological gap, see ISOCAM
3	P1_4p85_UM	4.8	3.14	0.159	4.1	Continuum
4	P1_7p3_UM	7.3	2.19	0.275	6.2	Continuum
5	P1_7p7_UM	7.7	9.32	0.249	6.4	PAH
6	P1_10_UM	10.0	5.55	0.345	8.4	sillicate feature
7	P1_11p3_UM	11.3	14.07	0.293	9.5	PAH
8	P1_12p8_UM	12.8	5.55	0.517	10.8	Continuum
9	P1_16p0_UM	15.0	5.33	0.354	13.8	Continuum
10	P1_11p5_UM	12.0	1.82	0.483	10.0	IRAS 12 ${\mu}$ m see ISOCAM
11	P2_20_UM	20.0	2.33	0.321	17.7	Close to Q band
12	P2_25_UM	25.0	2.61	0.375	20.0	IRAS 25 ${\mu}$ m
13	P3_60_UM	60.0	2.35	0.112	50.3	IRAS 60
14	P3_100_UM	100.0	2.59	0.305	83.9	IRAS 100

A.1.2 PHT-P apertures

The PHT-P apertures were located on the inner circle of Change Wheel II (CHW2). Each wheel position is indicated by an integer. In Table A.2 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	[]	[mm]	[ $10^{-8}$ sr]
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	0.5281	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 were located in the outer circle of Change Wheel II (CHW2). In Table A.3 the filter specifications corresponding to a Change Wheel II position have been listed. The values for the spectral resolution ( ${\lambda}_c/{\Delta}{\lambda}$ ) were measured in the laboratory. The point spread function factor for the fraction of the psf falling on the entire array ( $f_{PSF}^{array}$ , Laureijs 1999, [32]) and the system responses ( $R_{mean}$ ) were derived from in-flight data. The values of $f_{PSF}^{array}$ and those of $f_{PSF}$ (Tables 2.3 and 2.8) are included in Cal G files PPPSF and PCPSF (Section 14.18). 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 Moneti, Metcalfe & Schulz 1997, [39]).

The point spread function factor represents the fraction of the power in the beam falling on the whole detector array if the beam is centred on the array (the values have been derived from in-flight data, see Chapter 10 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	1.73	0.759		wide band cont.(backup)
3	C100_50_UM	65	1.13	0.044	0.799 $\pm$ 0.006	continuum
4	C100_60_UM	60	2.51	0.130	0.782 $\pm$ 0.004	continuum IRAS 60 ${\mu}$ m
5	C100_70_UM	80	1.67	0.122	0.831 $\pm$ 0.007	continuum
6	C100_100_UM	100	2.18	0.268	0.757 $\pm$ 0.008	continuum IRAS 100 ${\mu}$ m
7	C100_105_UM	105	2.79	0.236	0.764 $\pm$ 0.010	continuum
8	C100_90_UM	90	1.69	0.296	0.759 $\pm$ 0.008	wide band continuum
9	C200_160_UM	170	1.94	0.425	0.512 $\pm$ 0.020	wide band continuum
10	C200_200_UM	200	3.55	0.219	0.667 $\pm$ 0.019	continuum
11	C200_180_UM	180	2.63	0.327	0.601 $\pm$ 0.045	continuum
12	C200_135_UM	150	1.91	0.259	0.552 $\pm$ 0.028	continuum
13	C200_120_UM	120	2.40	0.131	0.489 $\pm$ 0.028	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 Table A.4 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