The measured wavelength locations of the ETM+ spectral bands are compared to Landat 5’s TM in Table 8.1 The spectral bandwidths are determined by the combined response of all optical path mirrors (i.e. primary, secondary, scan line corrector, scanning), the spectral filters, and the individual detectors. The spectral filters, located immediately in front of each detector array, are the dominant items that establish the optical bandpass for each spectral band. The prime focal plane assembly has a filter housing that contains filters for bands 1 through 4 and the panchromatic band. The cold focal plane assembly has a filter housing that contains filters for bands 5 through 7.

Table 8.1 TM and ETM+ Spectral Bandwidths
Bandwidth (µ) Full Width – Half Maximum
Sensor Band 1
Plot
Data
Band 2
Plot
Data
Band 3
Plot
Data
Band 4
Plot
Data
Band 5
Plot
Data
Band 6
Plot
Data
Band 7
Plot
Data
Band 8
Plot
Data
TM 0.45 – 0.52 0.52 – 0.60 0.63 – 0.69 0.76 – 0.90 1.55 – 1.75 10.4 – 12.5 2.08 – 2.35 N/A
ETM + 0.45 – 0.52 0.53 – 0.61 0.63 – 0.69 0.78 – 0.90 1.55 – 1.75 10.4 – 12.5 2.09 – 2.35 .52 – .90

A discrete spectral shift occurred on Landsat 5 TM has been largely attributed to filter outgassing. The ETM+ filters were made using a process called ion assisted deposition (IAD) which presumably makes the filters resistant to this phenomenon. In addition, the new filters have shown significant improvement in band edge responses as compared to Landsats 4 and 5.