Last month I reported Hobbyists Plan to Reboot NASA Spacecraft, outlining their efforts to contact ISEE-3 and change its course. With assistance from volunteers, the Arecibo Radio Astronomy Observatory's 305-meter antenna and NASA's Deep Space Network (DSN) they have made great progress. Since early June, they've been able to send commands to the satellite. An analysis of telemetry from the ISEE-3 showed it is in great shape for a satellite launched 36 years ago—it has a power margin of 28 Watts using only the solar array. The battery died decades ago.
Before the group can fire the thrusters on ISEE-3 to change its course, they need to define its present orbit as accurately as possible. The plan is to use NASA's DSN for ranging. The group wasn't able to establish communications with ISEE-3 this Wednesday, but will try again on Sunday, according to the Space College ISEE-3 Project page. Once ranging is complete, they plan to briefly fire two thrusters to spin ISEE-3 up from its current 19.16 rpm to 19.733 rpm.
A software-defined radio built on an Ettus N200 and SBX motherboard is being using to communicate with the satellite. John Malsbury describes How to Talk to a 36-year-old Space Probe (ISEE-3) with GNU Radio, a USRP, and a Big Dish on his webpage. He included a shot of the GNU Radio Companion (GRC) modulator using to talk to ISEE-3. See my article Software-Defined Radios Help Explore RF Spectrum for guidance on how to get started with GNU Radio.
It doesn't take a huge antenna to receive ISEE-3. The transponder signals on 2217.5 MHz (LHCP) and 2270.4 MHz (RHCP) have been detected with dishes as small as four feet in diameter. From the posting Detection of ISEE-3 With a 4.5 Meter Dish in Estonia, it looks as if Viljo Allik, ES5PC, was using the HDSDR software and an Ettus N210 to receive the signals.
While the big dishes of NASA's DSN are still needed to communicate with ISEE-3, it’s amazing what can be done with off-the-shelf hardware and open-source software today. While it's unlikely anyone will ever pick up ISEE-3 using one of the inexpensive RTL-SDR dongles, the three low-cost software-defined radio boards Taylor Killian described in his August 2013 article SDR Showdown: HackRF vs. bladeRF vs. USRP are all capable of tuning to the ISEE-3 frequencies.