Short answer
Yes, what you see in the news are recent images. It takes about 1 hour to the probe to send one image bit by bit, and about 4 hours for the bits to travel from the probe to Earth.
If New Horizons could do the scientific work, take images, and send them at the same time, this would be great, but that's not the case. While the probe had more time available for transmitting images in the previous days, now that the probe is close to Pluto and its moons the high-priority task is to collect scientific data (including images) and store them aboard the probe.
Data will be downloaded to Earth as other activities permit. Many more images are coming, some in the following days, but at only 1 image per hour, this will take months, so an image shot today might be transmitted to Earth only in several months.
All the details in the following full (and long) answer!
Source.
How slow is the communication between New Horizons and Earth?
From Wikipedia:
Communication with the spacecraft is via X band. The craft had a
communication rate of 38 kbit/s at Jupiter; at Pluto's distance, a
rate of approximately 1 kbit/s is expected. Besides the low
bandwidth, Pluto's distance also causes a latency of about 4.5
hours (one-way). The 70 m (230 ft) NASA Deep Space Network (DSN)
dishes are used to relay commands once it is beyond Jupiter.
It says that the traffic between the probe and the Earth is possible at about 1 kb/s. So to transmit an image it takes time: 1 kilobit image will take more or less 8 seconds, 1 megabit will take 1,000 seconds or 17 mn, etc.
(That's not completely accurate because additional control and correction bits are added to the pixel bits. But this is the principle.)
How long does it take to send an image file?
A LORRI image can be compressed aboard New Horizons, down to the size of 2.5 Mbits (depending on the content of the image). It takes about 42 mn to send this from the probe. But the signal has yet to travel to Earth. . . .
How long does it take to receive the image file?
Pluto and New Horizons are now at a distance of about 4.6 billion km. The radio waves travel at about 300,000 km/s. So it takes 4h20 to get to Earth.
To sum up:
- T0: New Horizons sends the first bit of an image and continues sending bits during 42 mn
- T0 + 42 mn: New Horizons sends the next image, and at T0+84 mn another one, etc.
- T1 = T0 + 4h20: We receive the first bit of the first image on Earth.
- T1 + 42 mn: We get the last bit of the first image, and then the first bit of the next image, etc.
How many images can be received in a month?
It has taken 5h02 for the first image. The next image can be received, and will be complete 42 mn later.
At this rate we are capable of receiving 34 images per day. In a month we can get 1045 images.
But actually this will be done in two phases: A browse catalog will be sent first to Earth in medium compressed format like explained so far, then the larger full resolution images (lossless compression). This is the current schedule:
Are images currently sent?
using the downlink schedule provided by @TildalWave (now unavailable), you can see that images are currently sent:
- Today and tomorrow, there are medium compressed image sets named NY Times to be downloaded.
- High-resolution images will be sent planned 17-20th July.
Be ready to see them in the news!
This is very slow! Why?
New Horizons is very far, so we receive a very faint signal from it. To be able to decide if we are currently receiving a 0 or a 1 we need to accumulate received energy:
The information sent by the probe is constant for a bit duration. Some radio interference may corrupt the received value, and it may last more than the bit duration.
Thermal noise is added to the transmitted information, mostly by the receiver itself, this is always the case in radio-communications. This noise has a Gaussian distribution and a mean of zero.
The receiver is able to take the mean of the received signal, and therefore may eliminate the noise and recover the probe original information.
The larger the noise power compared to the bit information power, the more it is difficult to recover the faint underlying signal, this can be overcame by observing the bit information signal a longer time, hence the link data-rate must be smaller.
The error introduced by interference can be corrected using a correcting code, based on redundancy, slowing a bit more the data-rate.
The datarate is directly linked to the inverse of the SNR (signal/noise ratio), decreasing as the distance increases. The consequence is deep-space communications have a small throughput. Clever communication techniques constantly adjust the radio link, the modulation and the correcting code can be selected to be the most efficient for the current SNR. This allows to reach the theoretical datarate limit, known as Shannon limit, this is the principle behind turbocodes and many other applications like 5G cellphones.
Images cannot be sent continuously
New Horizons cannot send the images 24x7 to Earth:
- Sometimes the Earth is not visible
- Sometimes the antenna cannot be oriented in the direction of Earth (because the scientific instruments may need the probe to be oriented differently to work).
- Sometimes data other than images must be transmitted.
The most important parts of the mission in this current Pluto fly-by phase is:
- To collect data about the atmosphere. Pluto is moving away from the Sun, and so is cooling down, and its frozen particles atmosphere is going to change.
- To take pictures of Pluto and its moons. New Horizons is now very close Pluto, and can shoot very detailed images, at a level never equaled in the past.
If you look at the spacecraft at the beginning of this post, you can see that the antenna cannot be oriented (to Earth) without changing other instruments and sensors orientation too, and that the LORRI imager and the dish are 90° apart, which limits the direction for imaging while transmitting to Earth.
So the high-priority data will be collected (images and other sensors output), and stored in memory. Later, at appropriate times, the probe will be oriented for a "call home" activity, so that stored data can be downloaded to Earth.
Where do images land?
The images are received by the Deep Space Network (NASA) with antennas at 3 locations around the world. At this time this is Madrid which is looking to New Horizons with its largest antenna (diameter 70 m). But as you see there is no signal, the communication is not active.
