April 1980:the 71-degree Cosmos satellites

On 16 March 1967 - the fifth anniversary of the launch of the first Cosmos satellite - the Soviet Union launched Cosmos 148 into an orbit inclined at 71 degrees (to the equator), the first time that this inclination was used. In the period to 1977 this inclination was used for a few scientific flights, but the majority of the 72 launches were for military purposes. It is the intention of this review to look at this group of satellites and give a summaryof the data which is available.

Launch Vehicle and Launch Site

The non-recoverable Cosmos flights at 71 degrees used the smallest of the Soviet Union’s launch vehicles, the “B-1” (using the classification introduced by Dr. C. S. Sheldon II). This vehicle consists of the SS-4/Sandal launch vehicle with an orbital stage attached. The writer is presently working on a review of the Sandal programme to be published at a later date, and more details of the launch vehicle will be found there.

The flights came from the northern Plesetsk launch site,which for many years was used for primarily military flights (together with the civilian "Meteor” flights and their precursors).

Sub-Groups of Flights at 71°

There seem to be four sub-groups of flights in the 71° slot when one considers the orbital period. Three of the groups are distinctive (periods 92.2, 93.1 and 95.5 minutes) while the fourth group (period 91.3 minutes) might be somehow connected with the 92.2 minute missions which form the largest sub-group of the flights under consideration. It should be noted that the Sandal launch vehicle seems to have worked fairly accurately since the standard deviation in the perigee heights is ±4 km or less.

Group 1 Flights (Period 91.3 minutes)

There are three satellites in this group and the launches came early in the history of the 71° missions. The perigees are virtually the same as found in Groups 2 and 4 which follow,while the apogee is about 80 km below that found on the Group 2 flights. If these three missions had a wider range in the apogee heights one might consider that the launch vehicle failed to place them in the intended orbit, but this can clearly be ruled out.

It should be noted that the three missions came within three weeks of Group 2 missions, and it is possible that there might be some connection here. The missions concerned are given below, together with the period between the launches.

Cosmos 148 (Gp 1) Cosmos 152 (Gp 2) 9 days

Cosmos 242 (Gp 1) Cosmos 245 (Gp 2) 13 days

Cosmos 308 (Gp 1) Cosmos 311 (Gp 2) 20 days

Using a slightly modified version of the method for calculating orbital plane spacings described elsewhere the orbits of the Group 1 satellites were projected forward in time for a comparison with the (apparently) associated Group 2 flights. There seems to be no connecton between the pairs Cosmos 148/152 or Cosmos 242/245, but within the error bounds discussed in the following section it was found that Cosmos 308 was 60° ahead of Cosmos 311 and 90° behind Cosmos 303. Although the flights were at somewhat different altitudes and therefore the orbits precessed at different rates, the relative orbital plane spacings only changed slightly. The mean precession for the Group 1 flights was 2.701 °/day and the corresponding value for Group 2 flights was 2.626°/day, so in ten days the planes separated by only just over half a degree.

Group 2 Flights (Period 92.2 minutes)

This is by far the largest of the four groups considered here,being 52 missions or 72% of the Cosmos 71 ° programme. The perigee altitudes were virtually constant at around 270 km, but the apogees ranged from 462 km (Cosmos 257) to 514 km (Cosmos 481 and Cosmos 745), where the orbits are taken from the Royal Aircraft Establishment’s satellite tables. The apogee altitude varied in a random manner, and does not seem to be connected with the date of launch. The orbits chosen for this group of satellites was such that they repeated their ground track after 31 orbits. At the programme’s peak there were about seven flights of these satellites per year, and when the flights ended after Cosmos 850 (1976) no obvious successor appeared for what seems to have been an important programme.

The planes of the satellite orbits were checked to see whether any significant spacings appeared. Here, a "significant spacing” is one which is a factor of 360°, those usually being looked for being 0°, ±30°, ±45°, ±60°, ±90°, ±120° and 180°.

Group 3 Flights (Period 93.1 minutes)

The third group to be considered consists of three satellites,Cosmos 261, Cosmos 348 and Intercosmos 8 (the first Inter-cosmos launch from Plesetsk) and these flights have been identified as scientific. In fact, the two Cosmos flights would perhaps have been given the Intercosmos name if they had not gone from Plesetsk which at that time was not open to foreign scientists. The first two flights were studying the aurorae whilethe Intercosmos studied the ionosphere.

Calculations show that the orbits for these three missions were chosen to allow the ground track to repeat after 92 orbits (nearly six days). The Cosmos flights had lifetimes of 54 days (Cosmos 261) and 42 days (Cosmos 348), while the Intercosmos had a lifetime of 92 days, the longer lifetime possibly reflecting the change in solar activity when the third flight was made.

Group 4 Flights (Period 95.5 minutes)

The fourth and final group of the Cosmos 71 ° missions consists of fourteen flights from 1968 to 1977, the last launch (Cosmos 919) being the final orbital use of the Sandal launch vehicle. It will be noted from that the range of apogee values found on the flights is greater than that found for any of the other three groups, while the perigee range is about the same as for the Group 1 and Group 2 flights. However, when the standard deviation is expressed as a percentage of the mean apogee it comes to 2.8%, compared with 2.9% for the Group 2 missions. The actual range of apogee is from 780 km (Cosmos 275) to 865 km (Cosmos 849). The orbits of these flights were chosen to allow the ground track virtually to repeat daily, the longitude differing by nearly 1.5° in just less than a day. However, this is for an average orbit, and individual satellites deviated from this slightly.

Just as the Group 2 flights ended in 1976, the Group 4 flights finished the following year, although here there seems to be the hint of the Skean being used for an upgraded programme. Cosmos 687 and Cosmos 822 were launched in 1974 and 1976 respectively into 280/700 km orbits inclined at 74°. Although no further flights have been made, one is led to wonder whether these two flights might have been part of an intended follow-on programme which has yet to materialise.

Purpose of the Flights

It was noted in the Introduction to this review that only a very few of the satellites discussed have had scientific missions announced, and therefore it would seem logical to assume that the main programme for the Cosmos flights at 71 ° was military. Even two of the flights which have had scientific missions announced (Cosmos 321 and 481 in Group 2) seem to have been primarily military in nature.

When looking at the Soviet military space programme one looks for parallels with the American programme, some details of which are available in “open” sources. The Cosmos 71° flights are normally thought to be military ferret flights, and here we have a difficulty in that there is very little information available dealing with the American flights which are assumed to have a similar nature. Sheldon has listed these Cosmos flights as simply “minor military” without going further than this, and Jasani suggests a ferret role without being more specific.

One interesting theory for the flights has been put forward by Phil Klass, who is the senior avionics editor of the respected Aviation Week & Space Technology magazine. Klass has suggested that the flights, together with similar missions launched from Kapustin Yar into 48° and 49° orbits, formed a crude cloud-cover sensing system. Klass sees the flights as supporting the large recoverable reconnaissance satellites in that the smaller satellites could provide weather information over proposed “targets” so that an expensive recoverable flight would not be launched if the target were to be under cloud and therefore unobservable. He notes that the Royal Aircraft Establishment’s “order of magnitude” dimensions for the Cosmos flights - ellipsoid, 400 kg mass, 1.8 m long, 1.2 m diameter - are roughly akin to those found in the Luna 3 probe which took the first pictures of the hidden side of the Moon in 1959. Luna 3 was an ellipsoid, 1.32 m long, 1.19 m in diameter with a mass of 278 kg. Klass feels that the basic Luna 3 design was upgraded to give a slightly larger craft with more photographic capability to form a cloud-cover satellite for the military. Klass’s theory for these Cosmos flights is the most specific to be found in the “open” press.

Follow-on Flights

It is obvious that the series of flights at 71° was important from the launch rate when the programme was in full swing. It is therefore surprising that no obvious successor programme can be found with certainty, since - whatever the missions were - the need for some continuation flights surely exists. It has already been noted that two satellites launched by the Skean vehicle went into somewhat similar orbits, although the two flights came while the Sandal payloads were still being launched. Apart from the two Skean flights, no missions havebeen flown in orbits similar to the 71 ° missions.

In the 1970s the recoverable reconnaissance satellites launched by the Soviet Union have become more versatile with satellites having lifetimes of around two weeks taking the place of the original “8-day wonders”. In September 1975 Cosmos 758 was launched into a typical reconnaissance satellite orbit but at an inclination of 67.1 degrees. Although the initial flight was possibly unsuccessful, subsequent flights have remained in orbit for up to a month and presumably this fourth generation reconnaissance satellite will at some stage take the place of the current third generation missions. The fourth generation craft probably have masses of up to 7,000 kg.