A: No, LightCube will safely disintegrate in the upper atmosphere within a couple of years. Even at LightCube’s altitude (400 km), a small amount of air exists. This air generates drag which slowly lowers the spacecraft’s orbit and leads to a passive atmospheric reentry. As part of our licensing process we must show, via simulations, that everything burns up.
A: The goal is to be “visible” to most people on Earth. The human eye can see stars as faint as magnitude 6 (higher magnitudes are fainter). Stars in constellations and large satellites are visible on a night with no clouds. The current goal is for a LightCube flash to appear to the human eye at an apparent magnitude similar to the International Space Station (ISS), which has an apparent magnitude of about 0. Amateur astronomers in cities like Phoenix, can usually reach a limiting magnitude of about 18 with their telescopes (ClearDarkSky.com).
A: Light pollution is the presence of artificial light sources at night. The most common light pollution is caused by city lights that make it hard to see faint stars. More recently, astronomers have seen the effects of satellites orbiting Earth reflecting sunlight as they move into the nighttime. While satellites do not light up the ground appreciably, they do become visible in telescope images and often to the naked eye. LightCube does not contribute to either of these forms of light pollution. It is too small to reflect much sunlight to the ground. LightCube’s flash will look like an extra star in the sky for a brief moment. When it flashes, LightCube is as bright as a typical naked-eye satellite or star for about 8 microseconds. After each flash, LightCube takes 30 seconds to recharge. During this recharge time, it cannot flash. Under the most extreme case that LightCube is continuously commanded to flash (which is unlikely), LightCube would appear to someone on the ground as a “star” that blinks on briefly once every 30 seconds as it moves from the west horizon to the east horizon over a period of about 10 minutes. This would be like a visible satellite passing overhead, but with a duty cycle of less than 0.000027%.
A: Anyone will be able to trigger LightCube to flash its light by sending it a specific radio signal. Because LightCube moves quickly in its orbit, it experiences Doppler shifting of frequencies. LightCube will need to be nearly overhead in order for the radio signal to successfully trigger it. After it launches, several commonly available smartphone and computer apps will be able to show when LightCube is overhead. Using a handheld radio equipped with a number pad and a small antenna you will transmit a predefined number code. If LightCube is charged, it will flash. The tracking app will also help you know approximately where to look in the sky to see LightCube’s flash. We will post a recommended radio setup and more detailed instructions before LightCube launches.
A: Yes. Regulations vary around the world, but in most locations you will need an amateur radio license to send a signal. LightCube will operate in the amateur band at a frequency coordinated by the IARU.
A: If its capacitor bank is charged, LightCube flashes when it receives a flash request (by radio signal) from an amateur user. A flash lasts for 8 microseconds (a microsecond is one millionth of a second, or 0.000001 seconds). After each flash, LightCube takes 30 seconds to recharge. It cannot flash during this time. In the most extreme scenario, if LightCube receives continuous flash requests, it will flash briefly once every 30 seconds. Given its expected orbital properties and velocity, if flashes are continuously commanded, then consecutive flashes would be spaced about 2 degrees apart in the sky. However, it is unlikely that LightCube will continuously receive flash commands, so in most cases flashes will be much farther apart.
A: Most telescopes have a field of view smaller than 1 square degree. The odds that LightCube is in this field of view at any moment are less than 1 in 20,000. The odds that it is in the field and flashing at any moment are at most 1 in 1011 because it can only flash for a brief moment at most once every 30 seconds. The odds of seeing LightCube go up the longer you observe, but stay very small. After 8 hours of observing, the chances of seeing a flash from LightCube in your telescope are at most 6 in 109, slightly better than the odds of winning the Arizona lottery. LightCube moves at least 2 degrees between the closest possible neighboring flashes.
A: The Vera Rubin Observatory (VRO) anticipates its initial operations, often called “first light”, will commence in early 2023. It will have a 9.6 square degree field of view and a pixel size of 0.2 arcseconds with expected seeing of 0.7 arcseconds. Typical exposures will likely be about 30 seconds long. The odds of VRO seeing a LightCube flash in any given exposure are less than 4 in 109. If VRO does catch a LightCube pulse, it will appear mostly in a small, localized group of pixels because LightCube’s short flash duration is below the 10 millisecond timescale of atmospheric turbulence and the motion of the cubesat during the flash yields only a short 0.002 arcsecond streak on the sky. LightCube’s 8 microsecond pulse is much shorter than a typical VRO exposure. This will make LightCube’s pulse appear 6 magnitudes fainter in the exposure compared to how it is perceived by the human eye. It is unlikely that multiple exposures would capture LightCube pulses on a single pass over the VRO. LightCube’s ephemeris will be included in the database of objects known to the VRO.
A: Yes! It is telling you that someone has just sent a ping. If you sent a ping and saw a flash, it was probably you!
A: The current plan is to launch late in 2022.
A: Several cubesats have attempted to produce visible lights. Fitsat (2013), built by students at Fukuoka Institute of Technology, used high power LEDs to transmit Morse code. It was 8th magnitude and visible with binoculars. Equisat (2016) was built by students at Brown to produce a naked eye beacon.
A: Yes, optical lasers transmitted from observatories have long been used to drive adaptive optics. Direct transmission beacons from orbit would reduce some sources of uncertainty due to the double path and reflection. Orbiting beacons have been proposed (Windhorst et al 2021). There are probably a lot of other things that could be done, for example in atmospheric chemistry.