66

Well, it is very common indeed to regain communications with a space probe after losing contact. In fact, communications are generally not continuous for the entirety of any mission. These are generally planned, for example This happened with almost each and every satellite at the beginning of the space age. Both the former USSR and the US are huge ...


52

Chandrayaan-1 hit the Moon at high speed and did not survive its "landing", which would have been much more difficult to engineer. (Its successor, Chandrayaan-2, which will actually land, is expected to cost \$125 million and has taken more than ten years so far, as opposed to the three years for Chandrayaan-1.) As far as cost goes, besides India's own (...


20

Are there any space probes\landers which regain communication after being lost? IMAGE Contact was lost with IMAGE on December 18, 2005, 07:39 UTC and it was detected again by amateur satellite hunter Scott Tilley on January 20, 2018. You can read more about it in that Wikipedia article and this answer and this answer SOHO SOHO was nearly lost. ...


16

It was not a thermal image at all. It is an optical image that has been captured by Orbiter of the lander spot and not thermal image as reported by others media houses. OHRC is same like our human eye. Since it consists of only one spectral band in visible region, so Image will be of gray scale, Not color image. https://twitter.com/Madrassan_Pinky/...


13

Orbiting satellites can still have problems with eclipses, from loss of both power and heat but the total time is normally measured in minutes so simply having enough battery power to keep electronics running (and producing heat) and some basic insulation will allow temperature control. For unlit periods in days heat from nuclear decay is often used, ...


12

I think a somewhat reasonable first-order analysis would look at the fates of similar hard impact failures on the moon and in deep space. The most immediately relevant is the failure of Israel's Beresheet lander, which failed similarly during landing. Beresheet was much smaller and lighter, so the hard impact resulted in total loss of mission. I think the ...


10

The degree of orbital shadowing experienced by an orbiting object with small orbital altitude is determined by its beta angle (normally used in reference to LEO objects but the concept applies to lunar orbiters as well). The angle is taken between the satellite's orbital plane and the vector to the Sun. Depending on the value of the beta angle, a satellite ...


8

Did the cold temperature of the lunar south pole cause Chandrayaan-2's on board electronics to fail? tl;dr: Probably not, the spacecraft was likely in sunshine at the time, and would have also been built and insulated to withstand regular short eclipses. Currently we don't know what happened, or if the mission is lost. At the time of the second ...


8

LRO was inserted into a polar frozen orbit for commissioning, which required no stationkeeping. This orbit was a stable 31.5 km x 199 km polar orbit with periapsis over the South Pole. By "frozen" they mean that the line of apsides and eccentricity remain fixed. It then moved into a 50km circular polar orbit (+/- 20 km) for its science mission. This ...


8

It didn't have enough thrust. Small rocket engines are easier to build than large ones, and weigh a lot less. That probe (I assume you mean Chandrayaan 1) had a 440 N main thruster that it used to get to Lunar orbit. It weighed initially about 1350 kg all from wiki. That amounts to an acceleration of approximately 0.3 m/s/s. You need around 4000 m/s for ...


7

How has life of the orbiter increased from 1 year to more than 7 years? The stated one year operational period represented the pre-mission plan. That pre-mission plan had to provide enough delta V to transfer the vehicle from an insertion orbit to a more eccentric Earth orbit, then to a lunar transfer orbit, then to an eccentric lunar orbit, then to a ...


7

There is no circular orbit that has a share of 50:50 between night and day. The possible times are a bit less than 50% to 0% night or, respectively, a bit more than 50% day to 100% day. The two extreme cases are: an orbit that is aligned with the terminator (the border between night and day on the surface) is in perpetual daylight. an orbit that passes ...


7

(Placeholder answer: somebody should be able to do a better write-up. Posted because it contradicts the other answer, putting it here allows it to be voted down if it is incorrect) It's taking advantage of the Oberth effect to save fuel. By raising the orbit in several stages the Oberth effect is increased. In addition, raising the orbit in several steps ...


6

For the embedded software, likely Ada An ISRO scientist working out of the Atmospheric and Oceanic Sciences group gave some insight that his part of ISRO mostly works with FORTRAN, MATLAB and Python - but that ISRO doesn't really have a standard language for its projects. It's a big agency with a lot of facilities involved in many different projects. ...


6

Thanks to @jkavalik for the informative answer and helpful links! As is pointed out there, there seems to be an abundance of false social media accounts claiming to be K. Silvan. From today's Sep 09, 2019 post: Regarding Social Media Accounts in the name of Kailasavadivoo Sivan, Chairman ISRO: It has been noted that social media accounts in the name of ...


5

It all depends on how you define "dayside" and "nightside", and how you define "entering" or "exiting" either one of them for a satellite. I suppose a big part of the confusion comes from this statement: Being in a polar orbit, Chandrayaan-2 enters the dayside of the Moon crossing the north pole, traverses through the dayside and enters the nightside ...


5

The explanation has to do with the operation of the radar transmitters and the round trip light travel time. It takes about 3 seconds for a radar pulse to travel from the Earth to the Moon and back. The planetary radar transmitters are high power; the Goldstone transmitter (at full strength) is 500 kW, the Arecibo transmitter is nearly 1000 kW. By ...


5

It will be a combination of things. Like TonyK mentioned in his comments, most of the change will occur during cis-lunar transfer. This is optimal because inter-planetary trajectories can be designed to result in an optimal parking orbit around your target planetary body. One neat trick astrodynamists use is B-plane targeting (a nice AGI article here: http://...


5

Not meeting the criteria of the question but there is day probe from Pioneer which was not intended to survive but continued to operate for 45 minutes after impact. A number of other probes have lost contact for various software related reasons, including the voyagers but being software recovery is more possible than for a lander suffering some form of ...


4

Need to mention Akatsuki probe, which lost contact for an hour instead of 20 minutes entering Venus orbit in 2010. This incident led to five year delay in achieving destination.


3

I know nothing of the activity you're asking about, but I do know something about radar. All the radar systems I've worked with used a single antenna to both transmit and receive. The power of the transmitter is very large compared to the return echo that needs to be received, and the very sensitive receiver needs to be disconnected from the antenna when ...


3

The multi-revolution transfer orbits can be called as 'Phasing elliptical orbits'. In the mission planning, it gives us some advantage such as reducing the finite burn arc losses which may depending on the particular cases to about 80 m/s that can translate directly to savings in mass. Such transfers also give us good time to characterize the propulsion ...


2

I think the it refers to Pragyaan. Pragyaan communication is via Lander to IDSN(and DSN) and Lander will have 15 days visibility. Orbiter is in polar orbit of about ~2 Hrs and the orbit is not in anyway earth synchronous. We do experience eclipse and data silence every orbit.


2

Since the deep space network can perform ranging on spacecraft much farther away (tens of thousands of times farther than the moon) by itself, why was it necessary to use a non-colocated, non-DSN dish to receive signals in this case? The ranging you're referring to is cooperative radio ranging: The DSN sends a signal to the spacecraft, the spacecraft ...


1

Now that's it's been a few months... according to Lok Sabha (a representative of the Indian Department of Space): During the second phase of descent, the reduction in velocity was more than the designated value. Due to this deviation, the initial conditions at the start of the fine braking phase were beyond the designated parameters. As a result, Vikram ...


1

A study on such transfers requires the knowledge of : Optimal Control Theory and Optimal space trajectories https://www.elsevier.com/books/optimal-space-trajectories/marec/978-0-444-41812-8 This book would take a lot of time , but enables you with knowledge to do simple study of such missions Well you should be looking for optimization of fuel as the ...


1

The lifetime probably didn't increase. Only the estimate increased. Due to uncertainties in any space mission we tend to err on the side of conservatism when advertising mission life; if we are fortunate we later add to the mission. The NASA Mars rovers Spirit and Opportunity were "supposed to" last 90 days or 90 sols (not sure which), we all know how ...


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