Especially the camera on the helicopter could be a great success with spectacular views !
Hobbes' answer explains why live broadcast is currently not feasible from the Mars side. I'd like to complement it with why this is currently not feasible from the Earth side.
Mars power budgets are not generous, so by the time spacecraft transmissions get back to Earth they are incredibly faint. The only equipment used to reliably receive these signals is the Deep Space Network (or DSN), the largest and most sensitive scientific telecommunications system in the world.
Here's why this is a problem:
- The DSN has only 3 of the large 70m antennas (and you need the large ones for high data rates), which have to collectively cover all deep space missions (including Mars) for all countries which partner with NASA. Granted, each dish can be in contact with more than one mission at a time (there's an excellent page maintained by JPL indicating who is in active contact), but time is at a premium.
- Consequently, DSN time is very expensive. This question suggests costs of close to 5000 dollars an hour, plus setup and tear down fees.
- While there are 3 dishes, only one is going to be pointing at Mars at any given time, and there are a lot of Mars missions. Consequently slots are also at a premium. In fact, this issue is a real concern given the glut of Mars missions coming up in 2020.
Now, you might suggest "we shouldn't care how expensive or how exclusive it is, this is a flagship class mission" and these sorts of calls certainly do happen. The Mars Reconnaissance Orbiter commands 16 hours a day of DSN time. However, the Mars Reconnaissance Orbiter also states that this link tops out at 4 megabits per second (worst case is 500 kbps), which leads us to the nail in the coffin:
- Best-case data rates from Mars are on the order of 4 Mbps, whereas compressed-with-H.264 720p video needs 12 Mbps and 1080p needs closer to 22 Mbps. This rate from Mars is only achievable for a few months at closest approach. You would need to increase the link speed by a factor of at least 3 to get live, HD video even then.
Now, pre-recorded HD video is a different problem entirely, and is certainly feasible given enough local storage on the spacecraft and enough time to send it back to Earth bit-by-bit.
Edit -- As @Baldrickk points out in the comments:
The answer you link to is for very high quality video. Lossy video can be a lot lower in bandwidth. from en.wikipedia.org/wiki/Bit_rate: 2.5 Mbit/s YouTube 720p videos (using H.264) 4.5 Mbit/s YouTube 1080p videos (using H.264) so if you dropped the compression quality a little more than YouTube uses, 4Mb/s would be enough for 1080p content.
The question then becomes where OP wants to draw the line for "live HD television", but it's fair to say that on data rates alone, HD-ish video could be plausible.
That said, other obstacles on both the Mars and Earth side remain, and I don't believe the Mars 2020 mission will have live video.
The JPL Mars Helicopter Scout transmitter can send data at up to 250 kb/s, an order of magnitude short for HD video.
Communications with the rover are through a radio link called Zig-Bee, a standard 900 MHz chipset that will be mounted in both the rover and helicopter. The communication system is designed to relay data at 250 kb/s over distances of up to 1,000 m.
Live broadcasts from Mars' surface are limited by the time an orbiter is overhead (so a few minutes per day).
"an extra channel" sounds a lot easier than it is. You'd have to add a new transmitter to the rover (impacting the mass and power budget for all other activities) and a new transmitter to the helicopter. Then you'd need a way to receive those broadcasts in parallel with the main science data, and current Mars orbiters aren't designed to do that. So you'd need a new orbiter as well, which costs a few hundred million.
No new orbiters have been planned, and the current ones are getting old.
in other words, no. Live broadcast is not feasible.
According to this specs page, Mars 2020 Rover will have three kinds of antenna: Ultra-High Frequency Antenna, X-band High-Gain Antenna, X-band Low-Gain Antenna. The one used to send data to Earth are the first two: UHF and the High Gain antenna, the Low Gain Antenna is used for receving data from Earth and it is the slowest of all.
UHF has transmission rates up to 2 megabits per second on the rover-to-orbiter relay link. Notice that the MRO orbiter can achieve 2Mb/s (or more) to Earth, so you can have, at least in theory, a 2Mb/s link from Mars to Earth using MRO. High Gain antenna can only reach 3000bits per second while talking directly to a 70m antenna of the Deep Space Network on Earth so while it doesn't need the orbiter, it is a lot slower.
So the faster transmission is 2Mb/s using UHF through a good orbiter that also has 2Mb/s (or more) to Earth.
According to Bear answer, an H264 720p video would need 12mbps, so 2 Mb/s is not enough for HD TV.
On top of this, as mentioned from other answers and comments:
- it won't be "live", in the sense it takes at least a few minutes to send data from Mars to Earth
- it might be online only for a limited time window (depending on how long the orbiter and rover can see each other and if DSN antennas are available)