According to available reports, a PSK31 transponder will also be operating on the ISS PCSAT2 in conjunction with other modes such as voice, packet, BBS and SSTV. However, since there are many devices involved, this operation will be coordinated so as to avoid mutual QRM with other modes.
However, it seems that PSK31 will be at the forefront in the coming period. This method of satellite operation eliminates the disadvantages of FM operation - mutual interference between stations and the use of disproportionate power.
PSK31 stations have an Uplink at 29.402 MHz +/- 1 kHz and a Downlink at 435.275 MHz +/- Doppler frequency shift in FM mode. So they transmit on a classic HF device switched to SSB and receive on a 70cm FM device.